Merge branch '18.0' of git@github.com:Dolibarr/dolibarr.git into 19.0

htdocs/core/class/CMailFile.class.php

@@ -1814,7 +1814,7 @@ class CMailFile
 		$matches = array();
 		preg_match_all('/(?:"|\')([^"\']+\.('.implode('|', $extensions).'))(?:"|\')/Ui', $this->html, $matches); // If "xxx.ext" or 'xxx.ext' found
 
-		if (!empty($matches)) {
+		if (!empty($matches) && !empty($matches[1])) {
 			$i = 0;
 			// We are interested in $matches[1] only (the second set of parenthesis into regex)
 			foreach ($matches[1] as $full) {