Added some lock statements to try to prevent an (unreproducible) NullReferenceException. (Whatever was null was somewhere in the Dictionary code. I can't tell if this would actually help, but it doesn't appear to hurt.)
Added some lock statements to try to prevent an (unreproducible) NullReferenceException. (Whatever was null was somewhere in the Dictionary code. I can't tell if this would actually help, but it doesn't appear to hurt.)

sillsdev/hearthis,sillsdev/hearthis,sillsdev/hearthis