Update RTLCSS.php

There is no check to see if $parts is an array with more than one element. So, line 358 can execute and generate a PHP notice.

Author: pgee70

src/MoodleHQ/RTLCSS/RTLCSS.php

@@ -354,7 +354,7 @@ protected function processTransformOrigin(Rule $rule) {
 
             $value = $parts[0];
             // The first value may be referencing top or bottom (y instead of x).
-            if (!is_object($value) && preg_match('/top|bottom/i', $value)) {
+            if (!is_object($value) && preg_match('/top|bottom/i', $value) && count($parts)>1) {
                 $value = $parts[1];
             }