Keyboard modifiers with quick navigation

The quick navigation key disrupted keybindings with keyboard modifiers,
like Ctrl-C for copy. This restricts the quick navigation only where no
keyboard modifiers are active.

Fixes #184

src/bitmessageqt/__init__.py

@@ -1510,7 +1510,8 @@ class MyForm(settingsmixin.SMainWindow):
                 else:
                     self.on_action_InboxTrash()
             event.ignore()
-        elif event.key() == QtCore.Qt.Key_N:
+        elif QtGui.QApplication.queryKeyboardModifiers() == QtCore.Qt.NoModifier:
+            if event.key() == QtCore.Qt.Key_N:
                 currentRow = messagelist.currentRow()
                 if currentRow < messagelist.rowCount() - 1:
                     messagelist.selectRow(currentRow + 1)