[ModelicaSystem] fix exception handling

* define specific exceptions

Author: syntron

OMPython/ModelicaSystem.py

@@ -597,7 +597,7 @@ def getContinuous(self, names=None):  # 4
                     try:
                         value = self.getSolutions(i)
                         self.continuouslist[i] = value[0][-1]
-                    except OMCSessionException as ex:
+                    except (OMCSessionException, ModelicaSystemError) as ex:
                         raise ModelicaSystemError(f"{i} could not be computed") from ex
                 return self.continuouslist