qtvcp -qcode editor: fix error with reloading with no program loaded

It's not really an error!

Author: c-morley

lib/python/qtvcp/widgets/gcode_editor.py

@@ -326,6 +326,8 @@ def new_text(self):
 
     def load_text(self, filepath):
         self.filepath = filepath
+        if filepath is None:
+            return
         try:
             fp = os.path.expanduser(filepath)
             with open(fp) as f:
@@ -334,6 +336,10 @@ def load_text(self, filepath):
             LOG.error("load_text(): {}".format(e))
             self.setText('')
             return
+        except Exception as e:
+            LOG.error("load_text(): {}".format(e))
+            self.setText('')
+            return
         self.ensureCursorVisible()
         self.SendScintilla(QsciScintilla.SCI_VERTICALCENTRECARET)
         self.setModified(False)