Merge pull request #1421 from MarkReeder/2.0-wip

Fixes Opera flickering on the collapse plugin when reset is called without specifying the size

js/bootstrap-collapse.js

@@ -71,7 +71,7 @@
 
       this.$element
         .removeClass('collapse')
-        [dimension](size || '')
+        [dimension](size || 'auto')
         [0].offsetWidth
 
       this.$element.addClass('collapse')