Don't blow up when VideoUrl.type is ''
Don't blow up when VideoUrl.type is ''

Also, assert in VideoUrl.save that type is not ''.

https://sentry.amara.org/amaraproduction/group/6116/

ujdhesa/unisubs,norayr/unisubs,norayr/unisubs,ReachingOut/unisubs,eloquence/unisubs,ReachingOut/unisubs,ofer43211/unisubs,ReachingOut/unisubs,norayr/unisubs,wevoice/wesub,norayr/unisubs,pculture/unisubs,wevoice/wesub,ofer43211/unisubs,wevoice/wesub,wevoice/wesub,ofer43211/unisubs,ujdhesa/unisubs,ujdhesa/unisubs,eloquence/unisubs,pculture/unisubs,eloquence/unisubs,ujdhesa/unisubs,ofer43211/unisubs,pculture/unisubs,pculture/unisubs,eloquence/unisubs,ReachingOut/unisubs