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

(cherry picked from commit 274d36a)

Author: vmcj

webapp/src/Twig/TwigExtension.php

@@ -1032,8 +1032,8 @@ 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;
         }