Fix huge MR exceptions. Fixed link to diff for it

app/models/merge_request.rb

@@ -214,9 +214,9 @@ class MergeRequest < ActiveRecord::Base
   end
   def dump_diffs(diffs)
-    if broken_diffs?
+    if diffs == broken_diffs
       broken_diffs
-    else
+    elsif diffs.respond_to?(:map)
       diffs.map(&:to_hash)
     end
   end
@@ -224,7 +224,7 @@ class MergeRequest < ActiveRecord::Base
   def load_diffs(raw)
     if raw == broken_diffs
       broken_diffs
-    else
+    elsif raw.respond_to?(:map)
       raw.map { |hash| Gitlab::Git::Diff.new(hash) }
     end
   end

app/views/merge_requests/show/_diffs.html.haml

@@ -4,7 +4,7 @@
   %h4.nothing_here_message
     Can't load diff.
     You can
-    = link_to "download it", project_merge_request_path(@project, @merge_request), format: :diff, class: "vlink"
+    = link_to "download it", project_merge_request_path(@project, @merge_request, format: :diff), class: "vlink"
     instead.
 - else
   %h4.nothing_here_message Nothing to merge