Fix and optimise code (#904)

* Fix bug in early error reporting in main init
* Update docstrings and optimise code in GuiMain
* Update docstrings and optimise code in Config
* Update docstrings and optimise code in common module
* Update docstrings and optimise code in main project classes
* Update the OptionState class
* Update the spell checker class
* Update the file converter classes and extend tests
* Update the about, merge, split and item editor classes and extend tests
* Update item editor test
* Update about dialog tests
* Some minor test cleanup
* Fix typo and add clarification in contributing guide

novelwriter/dialogs/itemeditor.py

@@ -57,7 +57,8 @@ class GuiItemEditor(QDialog):
 
         self.theItem = self.theProject.projTree[tHandle]
         if self.theItem is None:
-            self._doClose()
+            self.close()
+            return
 
         self.setWindowTitle(self.tr("Item Settings"))