From 7ce1e8f3616e192f9d83c04bc827ff1e74654889 Mon Sep 17 00:00:00 2001
From: "B. Endres" <endres@systopia.de>
Date: Thu, 1 Apr 2021 13:57:50 +0200
Subject: [PATCH] proposed fix/workaround for CORE-2502

---
 CRM/Contact/BAO/Query.php | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/CRM/Contact/BAO/Query.php b/CRM/Contact/BAO/Query.php
index b53ebface160..f581fe2558ac 100644
--- a/CRM/Contact/BAO/Query.php
+++ b/CRM/Contact/BAO/Query.php
@@ -3293,7 +3293,8 @@ public function tag(&$values) {
     $tagTree = CRM_Core_BAO_Tag::getChildTags();
     foreach ((array) $value as $tagID) {
       if (!empty($tagTree[$tagID])) {
-        $value = array_unique(array_merge($value, $tagTree[$tagID]));
+        // make sure value is an array here (see CORE-2502)
+        $value = array_unique(array_merge((array) $value, $tagTree[$tagID]));
       }
     }