Fix default avatar not showing.
Merge pull request #938 from oldhobbyist/fix-default_avatar

mbbdev / lunadev branches - Fix default avatar not showing.
#939 Fix vulnerability in ModernBB
Drop unused file
#935 Fix alignment issues in search results
#940 Fix issues with update check
#924 Tag ModernBB 3.5.1
Merge ModernBB 3.5.1 into Luna 0.0.0