Fix a potential crash in pyVaultImageNode.

Fixes a crash which can occur when attempting to fetch
an unsupported image type.

MOULOpenSourceClientPlugin/Plasma20/Sources/Plasma/FeatureLib/pfPython/pyVaultImageNode.cpp

@@ -171,6 +171,8 @@ PyObject* pyVaultImageNode::Image_GetImage( void )
 			else
 				fMipmapKey->RefObject();
 		}
+		else
+			PYTHON_RETURN_NONE;
 	}
 	
 	return pyImage::New(fMipmap);