fix: NPE when trying to open Quickfix in Problems view

+ Add null-check for `org.eclipse.lsp4j.CodeAction.getDiagnostics()`

Author: FlorianKroiss

org.eclipse.lsp4e/src/org/eclipse/lsp4e/operations/codeactions/CodeActionMarkerResolution.java

@@ -117,6 +117,10 @@ private ShowMessageRequestParams reportServerError(LanguageServerDefinition serv
 
 	@Override
 	public IMarker[] findOtherMarkers(IMarker[] markers) {
+		if (codeAction.getDiagnostics() == null) {
+			return new IMarker[0];
+		}
+
 		return Arrays.stream(markers).filter(marker -> {
 			try {
 				return codeAction.getDiagnostics()