AbstractRelated is accepts '' as valid by default

Author: Alexandre Gaigalas

library/Rules/AbstractRelated.php

@@ -66,10 +66,11 @@ public function check($input)
     public function validate($input)
     {
         $hasReference = $this->hasReference($input);
+
         if ($this->mandatory && !$hasReference) {
             return false;
         }
 
-        return $this->decision('validate', $hasReference, $input);
+        return $this->decision('validate', $hasReference, $input) || $this->getReferenceValue($input) === '';
     }
 }

tests/library/Respect/Validation/Rules/KeyTest.php

@@ -13,6 +13,16 @@ public function testArrayWithPresentKeyShouldReturnTrue()
         $this->assertTrue($validator->validate($obj));
     }
 
+    public function testArrayWithEmptyKeyShouldReturnTrue()
+    {
+        $validator = new Key('someEmptyKey');
+        $obj = array();
+        $obj['someEmptyKey'] = '';
+        $this->assertTrue($validator->assert($obj));
+        $this->assertTrue($validator->check($obj));
+        $this->assertTrue($validator->validate($obj));
+    }
+
     /**
      * @expectedException Respect\Validation\Exceptions\KeyException
      */