Set always string $filename on References

Author: Darkmet98

src/References.php

@@ -68,13 +68,10 @@ public function mergeWith(References $references): References
         $merged = clone $this;
 
         foreach ($references as $filename => $lines) {
-            if (empty($lines)) {
-                //Check the $filename type
-                if (gettype($filename) == "integer") {
-                    //Set string
-                    $filename = strval($filename);   
-                }
-
+            //Set filename always to string
+			$filename = (string) $filename;
+			
+			if (empty($lines)) {
                 $merged->add($filename);
                 continue;
             }