Fixed crashing save dialogs under Qt5

qt/base/app.py

@@ -196,5 +196,7 @@ class DupeGuru(QObject):
     
     def select_dest_file(self, prompt, extension):
         files = tr("{} file (*.{})").format(extension.upper(), extension)
-        return QFileDialog.getSaveFileName(self.resultWindow, prompt, '', files)
-    
+        destination, chosen_filter = QFileDialog.getSaveFileName(self.resultWindow, prompt, '', files)
+        if not destination.endswith('.{}'.format(extension)):
+            destination = '{}.{}'.format(destination, extension)
+        return destination

qt/base/result_window.py

@@ -285,7 +285,7 @@ class ResultWindow(QMainWindow):
     def saveResultsTriggered(self):
         title = tr("Select a file to save your results to")
         files = tr("dupeGuru Results (*.dupeguru)")
-        destination = QFileDialog.getSaveFileName(self, title, '', files)
+        destination, chosen_filter = QFileDialog.getSaveFileName(self, title, '', files)
         if destination:
             if not destination.endswith('.dupeguru'):
                 destination = '{}.dupeguru'.format(destination)