fix projection matrix so widget resizes properly

SketchWidget.py

@@ -64,6 +64,7 @@ class SketchWidget:
 
         glViewport(0, 0, width, height)
         glMatrixMode(GL_PROJECTION)
+        glLoadIdentity()
         glOrtho(0, width, 0, height, 1.0, -1.0)
 
         glMatrixMode(GL_MODELVIEW)