From 37482dd0e0329bdf5b47cfc7f58fa9819c15d813 Mon Sep 17 00:00:00 2001
From: Markus Staab <maggus.staab@googlemail.com>
Date: Wed, 21 Dec 2022 10:09:11 +0100
Subject: [PATCH] fix php <=7.3

---
 src/Type/UnionTypeHelper.php | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/Type/UnionTypeHelper.php b/src/Type/UnionTypeHelper.php
index 7f8936899e8..28ec01b74a2 100644
--- a/src/Type/UnionTypeHelper.php
+++ b/src/Type/UnionTypeHelper.php
@@ -70,6 +70,10 @@ public static function getConstantStrings(array $types): array
 			$strings[] = $type->getConstantStrings();
 		}
 
+        if ($strings === []) {
+            return [];
+        }
+
 		return array_merge(...$strings);
 	}