The fix implemented in 0.5.1 because of WP Core Issue #27853 has been
fixed in WP 3.9.1. This patch makes sure that fix is only active on
WP versions 3.9 or earlier (actually not yet tested, but should be fine!)

git-svn-id: https://plugins.svn.wordpress.org/wp-editor-widget/trunk@901490 b8457f37-d9ea-0310-8a92-e5e31aec5664