Fix obscure bug on updating custom fields (not necessarily hittable v…

…ia UI)

This fixes a bug which I think only applies to programatically created custom fields -basically if the field has an empty option_group_id
and then you update it to have one it does a check to see if the existing option_group_id is in use and does not handle the
fact the field is empty - leading to a mysql error.

CRM/Core/BAO/CustomField.php

@@ -2156,7 +2156,7 @@ public static function fixOptionGroups($customFieldId, $optionGroupId) {
     );
     // get the updated option group
     // if both are same return
-    if ($currentOptionGroupId == $optionGroupId) {
+    if (!$currentOptionGroupId || $currentOptionGroupId == $optionGroupId) {
       return;
     }
 

tests/phpunit/api/v3/CustomFieldTest.php

@@ -300,6 +300,28 @@ public function testCustomFieldExistingOptionGroup() {
     $this->assertEquals($optionGroupID, 3);
   }
 
+  /**
+   * Test adding an optionGroup to an existing field doesn't cause a fatal error.
+   *
+   * (this was happening due to a check running despite no existing option_group_id)
+   */
+  public function testUpdateCustomFieldAddOptionGroup() {
+    $customGroup = $this->customGroupCreate(['extends' => 'Organization', 'title' => 'test_group']);
+    $params = [
+      'custom_group_id' => $customGroup['id'],
+      'label' => 'Organization Gender',
+      'html_type' => 'Text',
+      'data_type' => 'Int',
+    ];
+
+    $customField = $this->callAPISuccess('custom_field', 'create', $params);
+    $this->callAPISuccess('CustomField', 'create', [
+      'option_group_id' => 3,
+      'id' => $customField['id'],
+      'html_type' => 'Select',
+    ]);
+  }
+
   /**
    * Test custom field get works & return param works
    */