[processing] Script decorators: correctly check that parent parameter exist

(cherry picked from commit f76be66)

Author: volaya

python/processing/algfactory.py

@@ -176,7 +176,7 @@ def _create_param(self, type, output=False, **kwargs):
             if parentname == name:
                 raise ProcessingAlgFactoryException("{} can't depend on itself. "
                                                     "We know QGIS is smart but it's not that smart".format(name))
-            if parentname not in self._inputs or parentname not in self._outputs:
+            if parentname not in self._inputs and parentname not in self._outputs:
                 raise ProcessingAlgFactoryException("Can't find parent named {}".format(parentname))
 
         kwargs['description'] = kwargs.pop("label", "")