Those two messages look like they are comming from the (as far as I can tell) new Blizzard error popup.
I've had Null come up before and it went away when I fixed other errors. The last one would imply that the ViragDevToolOptionsToggleButton template doesn't exist which would indicate a bug with ViragDevTools (a frame inheriting a template they've since deleted).
The Blizzard report is much more vigilant about templates existing/being duplicated and files listed in .toc and include .xml files existing (even commented out ones as it doesn't seem to check and ignore the -- anymore
)