fix(Condition): Fix array_pad() call with NULL values (#1340)

Author: Leksat

src/GraphQL/Resolver/Condition.php

@@ -37,7 +37,8 @@ public function __construct(array $branches) {
    */
   public function resolve($value, $args, ResolveContext $context, ResolveInfo $info, FieldContext $field) {
     $branches = $this->branches;
-    while ([$condition, $resolver] = array_pad(array_shift($branches), 2, NULL)) {
+    while ($branch = array_shift($branches)) {
+      [$condition, $resolver] = array_pad($branch, 2, NULL);
       if ($condition instanceof ResolverInterface) {
         if (($condition = $condition->resolve($value, $args, $context, $info, $field)) === NULL) {
           // Bail out early if a resolver returns NULL.

tests/src/Kernel/ResolverBuilderTest.php

@@ -231,6 +231,26 @@ public function testFromContext(): void {
     $this->assertResults($query, [], ['tree' => ['context' => ['myContext' => 'my context value']]]);
   }
 
+  /**
+   * @covers ::cond
+   */
+  public function testSingleCond(): void {
+    $this->mockResolver('Query', 'me', $this->builder->cond([
+      [
+        $this->builder->fromValue(FALSE),
+        $this->builder->fromValue('This should resolve into null.'),
+      ],
+    ]));
+
+    $query = <<<GQL
+      query {
+        me
+      }
+GQL;
+
+    $this->assertResults($query, [], ['me' => NULL]);
+  }
+
   /**
    * @covers ::cond
    */