Revert "[ModelicaSystem] remove OMCSessionException for now"

This reverts commit 2c3ab36.

Author: syntron

OMPython/ModelicaSystem.py

@@ -425,7 +425,7 @@ def getContinuous(self, names=None):  # 4
                     try:
                         value = self.getSolutions(i)
                         self.continuouslist[i] = value[0][-1]
-                    except Exception as ex:
+                    except OMCSessionException as ex:
                         raise ModelicaSystemError(f"{i} could not be computed") from ex
                 return self.continuouslist