Use the preg_match_all return to detect failures

Even if we cannot match anything we would have had an array containing an empty array. That array indicates that nothing was matched.

We should now fail when:
- preg_match_all fails
- preg_match_all returns it found 0 matches
- the redundant case (as safeguard) when the array has 0 matches

Author: vmcj

webapp/src/Twig/TwigExtension.php

@@ -1023,8 +1023,8 @@ public function hexColorToRGBA(string $text, float $opacity = 1): string
         if (is_null($col)) {
             return $text;
         }
-        preg_match_all("/[0-9A-Fa-f]{2}/", $col, $m);
-        if (!count($m)) {
+        $ret = preg_match_all("/[0-9A-Fa-f]{2}/", $col, $m);
+        if (!($ret && count($m[0]))) {
             return $text;
         }