Originally reported in http://es.wikipedia.org/w/index.php?title=Wikipedia:Caf%C3%A9/Portal/Archivo/T%C3%A9cnica/Actual&diff=41738883&oldid=41738850 when trying to debug a failing user script.
"My Firefox error console says the following: «Error: data is null
Source: http://bits.wikimedia.org/w/extensions/UsabilityInitiative/Vector/Vector.combined.min.js?283-12 Line: 33"
Version: unspecified
Severity: normal