Gerrit git cl: fix change-id appending.

git_footers.py

Index: git_footers.py
diff --git a/git_footers.py b/git_footers.py
index 1d4d4dd84099e5dcc95e78eb0870c10af3c437ae..4641f7470f551babbe8edb1938c21676e320f20d 100755
--- a/git_footers.py
+++ b/git_footers.py
@@ -83,9 +83,13 @@ def add_footer_change_id(message, change_id):
     if line == '' or line.isspace():
       break
     footer_lines.append(line)
+  else:
+    # The whole description was consisting of footers,
+    # which means those aren't footers.
+    footer_lines = []
   # footers order is from end to start of the message.
   footers = map(parse_footer, footer_lines)
-  if not all(footers):
+  if not footers or not all(footers):
     lines.append('')
     lines.append(change_id_line)
   else: