The issue was reported here:
Repro step:
- 
Have Discourse Gifs enabled on your theme
 - 
Try posting a new topic or reply
 - 
The JS error appears when the composer opens and prevents us from posting.
 
The issue was reported here:
Repro step:
Have Discourse Gifs enabled on your theme
Try posting a new topic or reply
The JS error appears when the composer opens and prevents us from posting.
I just merged this fix to the gifs plugin. Anyone affected will need to click the theme update button in their admin dashboard.
Sorry for the disruption!