Disable versions app JS in public mode

Since the version JS code isn't used in public link mode, disable it to
prevent Chrome freezing bugs due to the t() call being synchronous.

Fixes #4545

apps/files_versions/js/versions.js

@@ -1,5 +1,12 @@
 $(document).ready(function(){
 
+	if ($('#isPublic').val()){
+		// no versions actions in public mode
+		// beware of https://github.com/owncloud/core/issues/4545
+		// as enabling this might hang Chrome
+		return;
+	}
+
 	if (typeof FileActions !== 'undefined') {
 		// Add versions button to 'files/index.php'
 		FileActions.register(