- fixed bug in Gerber parser that allowed loading as Gerber of a file that is not a Gerber

- fixed a bug in extension detection for Gerber files that allowed in the filtered list files that extension *.gb*
- added a processEvents method in the Gerber parser parse_lines() method

FlatCAM.py

@@ -1,7 +1,7 @@
 import sys
 import os
 
-from PyQt5 import QtWidgets, QtGui
+from PyQt5 import QtWidgets
 from PyQt5.QtCore import QSettings, Qt
 from FlatCAMApp import App
 from flatcamGUI import VisPyPatches