MAGETWO-63736: 503 error when trying to make tax_class_id attribute Not Searchable

Author: rganin

app/code/Magento/Catalog/Controller/Adminhtml/Product/Attribute/Validate.php

@@ -154,7 +154,11 @@ private function setMessageToResponse($response, $messages)
      */
     private function checkUniqueOption(DataObject $response, array $options = null)
     {
-        if (is_array($options) && !$this->isUniqueAdminValues($options['value'], $options['delete'])) {
+        if (is_array($options)
+            && !empty($options['value'])
+            && !empty($options['delete'])
+            && !$this->isUniqueAdminValues($options['value'], $options['delete'])
+        ) {
             $this->setMessageToResponse($response, [__("The value of Admin must be unique.")]);
             $response->setError(true);
         }

app/code/Magento/Catalog/Test/Unit/Controller/Adminhtml/Product/Attribute/ValidateTest.php

@@ -198,8 +198,16 @@ public function testUniqueValidation(array $options, $isError)
     public function provideUniqueData()
     {
         return [
-            // valid options
-            [
+            'no values' => [
+                [
+                    'delete' => [
+                        "option_0" => "",
+                        "option_1" => "",
+                        "option_2" => "",
+                    ]
+                ], false
+            ],
+            'valid options' => [
                 [
                     'value' => [
                         "option_0" => [1, 0],
@@ -213,8 +221,7 @@ public function provideUniqueData()
                     ]
                 ], false
             ],
-            //with duplicate
-            [
+            'duplicate options' => [
                 [
                     'value' => [
                         "option_0" => [1, 0],
@@ -228,8 +235,7 @@ public function provideUniqueData()
                     ]
                 ], true
             ],
-            //with duplicate but deleted
-            [
+            'duplicate and deleted' => [
                 [
                     'value' => [
                         "option_0" => [1, 0],