[processing] Fix traceback when modeller parameter invalid value is detected

(cherry picked from commit 64bd9e5)

Author: nyalldawson

python/plugins/processing/modeler/ModelerParametersDialog.py

@@ -351,7 +351,9 @@ def createAlgorithm(self):
                 continue
             try:
                 wrapper = self.wrappers[param.name()]
-                if issubclass(wrapper.__class__, QgsProcessingModelerParameterWidget):
+                if issubclass(wrapper.__class__, WidgetWrapper):
+                    val = wrapper.value()
+                elif issubclass(wrapper.__class__, QgsProcessingModelerParameterWidget):
                     val = wrapper.value()
                 else:
                     val = wrapper.parameterValue()