Fix loadFromJSON 404s breaking fabric (Pattern)

Prevent image 404s in patterns from loadFromJSON from breaking
everything trying to get attributes of a source which is null, while
passing it upwards to allow dealing with images which failed to load
outside of Fabric.JS
Fix loadFromJSON 404s breaking fabric (Image)

Prevent image 404s in Images from loadFromJSON from breaking everything
trying to get attributes of a source which is null, while passing it
upwards to allow dealing with images which failed to load outside of
Fabric.JS Issue #1079
formatting for fixes
add spaces before {
Merge pull request #1212 from CapCap/master

Fix loadFromJSON 404s breaking fabric #1079