Fix #195: null values causing crashes

Author: jyapayne

main.py

@@ -1728,7 +1728,7 @@ def load_package_json(self, json_path=None):
         setting_list = super(MainWindow, self).load_package_json(json_path)
         for setting in setting_list:
             setting_field = self.find_child_by_name(setting.name)
-            if setting_field:
+            if setting_field and setting.value is not None:
                 if (setting.type == 'file' or
                         setting.type == 'string' or
                         setting.type == 'folder' or

util_classes.py

@@ -453,10 +453,10 @@ def __init__(self, name='', display_name=None, value=None,
 
     def filter_name(self, text):
         """Use the filter action to filter out invalid text"""
-        if hasattr(self.filter_action, text):
+        if text and hasattr(self.filter_action, text):
             action = getattr(self.filter_action, text)
             return action(text)
-        return text
+        return text or ''
 
     def get_file_information_from_url(self):
         """Extract the file information from the setting url"""