Fix argument replacement

Error on compiler Reference arguments: On default argument replacement, check the argument is a string before check his length is zero.

src/DependencyInjection/Compiler/AddDependencyCallsCompilerPass.php

@@ -438,7 +438,7 @@ private function replaceDefaultArguments(
             $declaredInParent = $parentDefinition && \array_key_exists($index, $parentArguments);
             $argumentValue = $declaredInParent ? $parentArguments[$index] : $arguments[$index];
 
-            if (null === $argumentValue || 0 === \strlen($argumentValue)) {
+            if (null === $argumentValue || (\is_string($argumentValue) && 0 === \strlen($argumentValue))) {
                 $arguments[$declaredInParent ? sprintf('index_%s', $index) : $index] = $value;
             }
         }