Prevent inheritance errors if imports fail

Author: jonoomph

src/windows/views/timeline_mixins.py

@@ -40,13 +40,15 @@
     from PyQt5.QtWebChannel import QWebChannel
     IS_WEBENGINE_VALID = True
 except ImportError:
+    QWebEngineView = object # Prevent inheritance errors
     IS_WEBENGINE_VALID = False
 
 try:
     # Attempt to import QtWebKit
     from PyQt5.QtWebKitWidgets import QWebView
     IS_WEBKIT_VALID = True
 except ImportError:
+    QWebView = object # Prevent inheritance errors
     IS_WEBKIT_VALID = False