From 17c6f98ba2096a6616b7af1a759ee5aa79546876 Mon Sep 17 00:00:00 2001
From: Maxime Rainville <maxime@silverstripe.com>
Date: Wed, 20 Jan 2021 12:23:09 +1300
Subject: [PATCH] BUG Fix PostgreSQL issue in TreeMultiselectField where field
 would try to filter list by a blank ID

---
 src/Forms/TreeMultiselectField.php           | 4 ++++
 tests/php/Forms/TreeMultiselectFieldTest.php | 7 +++++++
 2 files changed, 11 insertions(+)

diff --git a/src/Forms/TreeMultiselectField.php b/src/Forms/TreeMultiselectField.php
index 2857a5c30f1..de523dd392a 100644
--- a/src/Forms/TreeMultiselectField.php
+++ b/src/Forms/TreeMultiselectField.php
@@ -149,12 +149,16 @@ public function getItems()
 
         // Parse ids from value string / array
         $ids = [];
+
         if (is_string($value)) {
             $ids = preg_split("#\s*,\s*#", trim($value));
         } elseif (is_array($value)) {
             $ids = array_values($value);
         }
 
+        // Filter out empty strings
+        $ids = array_filter($ids);
+
         // No value
         if (empty($ids)) {
             return ArrayList::create();
diff --git a/tests/php/Forms/TreeMultiselectFieldTest.php b/tests/php/Forms/TreeMultiselectFieldTest.php
index 78d8b0190e7..c0d7ea2e94d 100644
--- a/tests/php/Forms/TreeMultiselectFieldTest.php
+++ b/tests/php/Forms/TreeMultiselectFieldTest.php
@@ -340,5 +340,12 @@ function ($folder) {
             [],
             $field->getItems()
         );
+
+        // Andle empty string none value
+        $field->setValue('');
+        $this->assertListEquals(
+            [],
+            $field->getItems()
+        );
     }
 }