Fix: Internal server error 500 for relationship to non-published post

src/class-config.php

@@ -689,12 +689,14 @@ protected function register_graphql_field( string $type_name, string $field_name
 								$post_object = get_post( $post_id );
 								if ( $post_object instanceof \WP_Post ) {
 									$post_model     = new Post( $post_object );
-									$relationship[] = $post_model;
+									if ( 'private' != $post_model->get_visibility() ) {
+										$relationship[] = $post_model;
+									}
 								}
 							}
 						}
 
-						return isset( $value ) ? $relationship : null;
+						return empty( $relationship ) ? null : $relationship;
 
 					},
 				];

tests/wpunit/ExplicitOptionsTest.php

@@ -89,6 +89,7 @@ public function testExplicitOptions() {
 				'show_in_graphql'     => true,
 				'graphql_single_name' => 'acfCpt',
 				'graphql_plural_name' => 'acfCpts',
+				'public'              => true,
 			]
 		);
 
@@ -148,7 +149,7 @@ public function testExplicitOptions() {
 			]
 		);
 
-		$expected_text_3 = 'test value2';
+		$expected_text_3 = 'test value3';
 		update_field( 'acf_text_field', $expected_text_3, $cpt_id );
 
 		// post assert validation.

tests/wpunit/PostObjectFieldsTest.php

@@ -1213,8 +1213,8 @@ public function testQueryMultipleSelectFieldWithNoValueSet() {
 	public function testQueryFieldOnCustomPostType() {
 
 		register_post_type( 'acf_test', [
-			'show_ui' => true,
-			'show_in_graphql' => 'true',
+			'public'              => true,
+			'show_in_graphql'     => 'true',
 			'graphql_single_name' => 'acfTest',
 			'graphql_plural_name' => 'acfTests'
 		] );