Fix for issues like #516

Fix a crash when a toolbar button does'nt exist. Now not appear, but no crash the js. Maybe some warn like "The button {blabla} not exists, not rendering" will be fine! But i don't want use the console.log/error that can crash in ie :/
Fix Travis CI

A space-failt at travis :(
Merge pull request #521 from eleazan/patch-2

Fix for issues like #516