[meld] filediff: Remove explicit None comparisons for chunks

[Kai Willadsen <kaiw src gnome org>]

commit 2f26a421cd206f150bd9f1807faaf61bf8de256a
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Thu Dec 21 06:13:53 2017 +1000

    filediff: Remove explicit None comparisons for chunks
    
    There's really no point, so just use truthiness.

 meld/filediff.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/meld/filediff.py b/meld/filediff.py
index 4b372e32..75e153d6 100644
--- a/meld/filediff.py
+++ b/meld/filediff.py
@@ -433,10 +433,10 @@ class FileDiff(melddoc.MeldDoc, gnomeglade.Component):
                 chunk2 = None
                 if self.num_panes == 3:
                     chunk2 = self.linediffer.get_chunk(chunk_id, 1, 2)
-                left_mid_exists = chunk0 is not None and chunk0[1] != chunk0[2]
-                left_exists = chunk0 is not None and chunk0[3] != chunk0[4]
-                right_mid_exists = chunk2 is not None and chunk2[1] != chunk2[2]
-                right_exists = chunk2 is not None and chunk2[3] != chunk2[4]
+                left_mid_exists = chunk0 and chunk0[1] != chunk0[2]
+                left_exists = chunk0 and chunk0[3] != chunk0[4]
+                right_mid_exists = chunk2 and chunk2[1] != chunk2[2]
+                right_exists = chunk2 and chunk2[3] != chunk2[4]
                 push_left = editable_left
                 push_right = editable_right
                 pull_left = editable and left_exists