pr-diffs: fixed a case when there are outdated comments and we're doing a rebase compare.

rhodecode/templates/codeblocks/diffs.mako

@@ -142,6 +142,8 b' collapse_all = len(diffset.files) > coll'
     %endif
 
     <div class="filediffs">
+    ## initial value could be marked as False later on
+    <% over_lines_changed_limit = False %>
     %for i, filediff in enumerate(diffset.files):
 
         <%