The code in the function matches() of class css_rule in cssimport.php was changed:

It did only work by coincidence if the string '$classString' was empty.
Now it's expecting such a situation and handles it explicitly.

Author: lpaulsen93

helper/cssimport.php

@@ -946,16 +946,22 @@ public function matches ($element, $classString, $media = NULL) {
         $classes = explode (' ', $classString);
 
         foreach ($this->selectors as $selector) {
-            foreach ($classes as $class) {
-                if ( $selector [0] == '.' && $selector == '.'.$class ) {
-                    $matches++;
-                    break;
-                } else {
-                    if ( $selector == $element || $selector == $element.'.'.$class ) {
+            if ( !empty($classString) ) {
+                foreach ($classes as $class) {
+                    if ( $selector [0] == '.' && $selector == '.'.$class ) {
                         $matches++;
                         break;
+                    } else {
+                        if ( $selector == $element || $selector == $element.'.'.$class ) {
+                            $matches++;
+                            break;
+                        }
                     }
                 }
+            } else {
+                if ( $selector == $element ) {
+                    $matches++;
+                }
             }
         }