UI:Fix. "Widget custom CSS editor" it was impossible to use base64

ui/src/vendor/css.js/css.js

@@ -147,7 +147,8 @@ fi.prototype.parseRules = function (rules) {
     rules = rules.split('\r\n').join('\n');
     var ret = [];
 
-    rules = rules.split(';');
+    // Split all rules but keep semicolon for base64 url data
+    rules = rules.split(/;(?!base64)/);
 
     //proccess rules line by line
     for (var i = 0; i < rules.length; i++) {