[meld] newdifftab: Fix blank-comparison regression from Gio changes

[Kai Willadsen <kaiw src gnome org>]

commit 35d01544cbed3c76f8700597f26630633d5f29c1
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Sat Apr 7 08:21:51 2018 +1000

    newdifftab: Fix blank-comparison regression from Gio changes

 meld/newdifftab.py | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)
---
diff --git a/meld/newdifftab.py b/meld/newdifftab.py
index 3309e6a2..f0c33b14 100644
--- a/meld/newdifftab.py
+++ b/meld/newdifftab.py
@@ -126,8 +126,14 @@ class NewDiffTab(LabeledObjectMixin, GObject.GObject, gnomeglade.Component):
         # TODO: This doesn't work the way I'd like for DirDiff and VCView.
         # It should do something similar to FileDiff; give a tab with empty
         # file entries and no comparison done.
-        compare_gfiles = [Gio.File.new_for_path("")] * self._get_num_paths()
-        tab = self.diff_methods[self.diff_type](compare_gfiles)
+
+        # File comparison wants None for its paths here. Folder mode
+        # needs an actual directory.
+        if self.diff_type == 0:
+            gfiles = [None] * self._get_num_paths()
+        else:
+            gfiles = [Gio.File.new_for_path("")] * self._get_num_paths()
+        tab = self.diff_methods[self.diff_type](gfiles)
         self.emit('diff-created', tab)
 
     def on_container_switch_in_event(self, *args):