minor fix for MIDAS importer

Author: briantoby

GSASII/GSASIIctrlGUI.py

@@ -10084,6 +10084,11 @@ def gitSwitch2DevBranch(event):
     to the develop (eventually to be renamed main) branch. 
     Complication here is that the GSASII.py file gets renamed 
     to G2.py so "shortcuts" need to be re-created to reference that. 
+
+    This is not yet "plumbed" into the current code, but it has been
+    tested with Windows and Mac. At some point this will be made part of the
+    update process in the master branch, but this routine is not needed in 
+    the develop (or eventially main) branch.
     '''
     G2frame = wx.App.GetMainTopWindow()
     gitInst = GSASIIpath.HowIsG2Installed()

GSASII/imports/G2pwd_MIDAS.py

@@ -56,6 +56,7 @@ def ContentsValidator(self, filename):
         '''Test if valid by seeing if the zarr module recognizes the file. Then
         get file type (currently Midas only)
         '''
+        fp = None
         try:
             fp = zarr.open(filename, 'r')
             if all([(i in fp) for i in self.midassections]): # are expected MIDAS sections present?