Switch to side-by-side view

--- a/Allura/allura/model/repo_refresh.py
+++ b/Allura/allura/model/repo_refresh.py
@@ -66,6 +66,7 @@
 
 def refresh_commit_trees(ci, cache):
     '''Refresh the list of trees included withn a commit'''
+    if ci.tree_id is None: return
     trees_doc = TreesDoc(dict(
             _id=ci._id,
             tree_ids = list(trees(ci.tree_id, cache))))
@@ -228,6 +229,7 @@
 
 def compute_diffs(repo_id, tree_cache, rhs_ci):
     '''compute simple differences between a commit and its first parent'''
+    if rhs_ci.tree_id is None: return
     def _walk_tree(tree, tree_index):
         for x in tree.blob_ids: yield x.id
         for x in tree.other_ids: yield x.id