[html2] Fix blank responses in html document (#18356)

* [html2]remove unnecessary mustache section

* [html2]add null check

Author: Aniokrait

modules/openapi-generator/src/main/resources/htmlDocs2/index.mustache

@@ -445,48 +445,49 @@
 
 
                             <div class="tab-content" id="responses-{{baseName}}-{{nickname}}-{{code}}-wrapper" style='margin-bottom: 10px;'>
-                              {{#schema}}
-                                <div class="tab-pane active" id="responses-{{baseName}}-{{nickname}}-{{code}}-schema">
-                                  <div id="responses-{{baseName}}-{{nickname}}-schema-{{code}}" class="exampleStyle">
-                                    <script>
-                                      $(document).ready(function() {
-                                        var schemaWrapper = {{{jsonSchema}}};
-                                        var schema = findNode('schema',schemaWrapper).schema;
-                                        if (!schema) {
-                                          schema = schemaWrapper.schema;
-                                        }
-                                        if (schema.$ref != null) {
-                                          schema = defsParser.$refs.get(schema.$ref);
-                                          Object.keys(schema.properties).forEach( (item) => {
-                                            if (schema.properties[item].$ref != null) {
-                                              schema.properties[item] = defsParser.$refs.get(schema.properties[item].$ref);
-                                            }
-                                          });
-                                        } else if (schema.items != null && schema.items.$ref != null) {
-                                            schema.items = defsParser.$refs.get(schema.items.$ref);
-                                        } else {
-                                          schemaWrapper.definitions = Object.assign({}, defs);
-                                          $RefParser.dereference(schemaWrapper).catch(function(err) {
-                                            console.log(err);
-                                          });
-                                        }
+                              <div class="tab-pane active" id="responses-{{baseName}}-{{nickname}}-{{code}}-schema">
+                                <div id="responses-{{baseName}}-{{nickname}}-schema-{{code}}" class="exampleStyle">
+                                  <script>
+                                    $(document).ready(function() {
+                                      var schemaWrapper = {{{jsonSchema}}};
+                                      var schema = findNode('schema',schemaWrapper).schema;
+                                      if (!schema) {
+                                        schema = schemaWrapper.schema;
+                                      }
+                                      if (schema == null) {
+                                        return;
+                                      }
+                                      if (schema.$ref != null) {
+                                        schema = defsParser.$refs.get(schema.$ref);
+                                        Object.keys(schema.properties).forEach( (item) => {
+                                          if (schema.properties[item].$ref != null) {
+                                            schema.properties[item] = defsParser.$refs.get(schema.properties[item].$ref);
+                                          }
+                                        });
+                                      } else if (schema.items != null && schema.items.$ref != null) {
+                                        schema.items = defsParser.$refs.get(schema.items.$ref);
+                                      } else {
+                                        schemaWrapper.definitions = Object.assign({}, defs);
+                                        $RefParser.dereference(schemaWrapper).catch(function(err) {
+                                          console.log(err);
+                                        });
+                                      }
 
-                                        var view = new JSONSchemaView(schema, 3);
-                                        $('#responses-{{baseName}}-{{nickname}}-{{code}}-schema-data').val(JSON.stringify(schema));
-                                        var result = $('#responses-{{baseName}}-{{nickname}}-schema-{{code}}');
-                                        result.empty();
-                                        result.append(view.render());
-                                      });
-                                    </script>
-                                  </div>
-                                  <input id='responses-{{baseName}}-{{nickname}}-{{code}}-schema-data' type='hidden' value=''></input>
+                                      var view = new JSONSchemaView(schema, 3);
+                                      $('#responses-{{baseName}}-{{nickname}}-{{code}}-schema-data').val(JSON.stringify(schema));
+                                      var result = $('#responses-{{baseName}}-{{nickname}}-schema-{{code}}');
+                                      result.empty();
+                                      result.append(view.render());
+                                    });
+                                  </script>
                                 </div>
-                                {{#examples}}
-                                  <div class="tab-pane" id="examples-{{baseName}}-{{nickname}}-{{code}}-example">
-                                    <pre class="prettyprint"><code class="json">{{example}}</code></pre>
-                                  </div>
-                                {{/examples}}
-                              {{/schema}}
+                                <input id='responses-{{baseName}}-{{nickname}}-{{code}}-schema-data' type='hidden' value=''></input>
+                              </div>
+                              {{#examples}}
+                                <div class="tab-pane" id="examples-{{baseName}}-{{nickname}}-{{code}}-example">
+                                  <pre class="prettyprint"><code class="json">{{example}}</code></pre>
+                                </div>
+                              {{/examples}}
                               {{#hasHeaders}}
                                   <div class="tab-pane" id="responses-{{nickname}}-{{code}}-headers">
                                       <table>