Fix unit test

src/Forms/GridField/GridFieldStateManager.php

@@ -42,7 +42,7 @@ class GridFieldStateManager implements GridFieldStateManagerInterface
         $value = $gridField->getState(false)->Value();
 
         // Using a JSON-encoded empty array as the blank value, to avoid changing Value() semantics in a minor release
-        if ($value === '[]') {
+        if ($value === '{}') {
             return $url;
         }
 

tests/php/Forms/GridField/GridFieldStateManagerTest.php

@@ -87,7 +87,7 @@ class GridFieldStateManagerTest extends SapphireTest
         $grid->getState()->initDefaults(['testValue' => 'foo']);
         $link = '/link-to/something';
 
-        $this->assertEquals('[]', $grid->getState(false)->Value());
+        $this->assertEquals('{}', $grid->getState(false)->Value());
 
         $this->assertEquals(
             '/link-to/something',

tests/php/Forms/GridField/GridStateTest.php

@@ -29,5 +29,4 @@ class GridStateTest extends SapphireTest
             'GridState with changes returns has a JSON object string for Value.'
         );
     }
-
 }