Avatar removed when updating signature

[isaak654]

Description

This was reported on the Bug Reports board:
https://www.simplemachines.org/community/index.php?topic=581644.0

Additional information/references

• 2.1.1 with no packages or addons, responsive theme blindspot
• Avatars are being deleted when users update their profile signature
• This seems to stem only from avatars chosen from gallery
• Tried clearing cache, logging out and back in, removing profile pic, saving and re-adding
• Nothing reported in error logs