Fix deprecation message if str_replace receive a null value in FormHelper (#689)

Author: ajira86

src/Kris/LaravelFormBuilder/Form.php

@@ -644,6 +644,10 @@ public function getName()
      **/
     public function getNameKey()
     {
+        if ($this->name === null) {
+            return '';
+        }
+
         return $this->formHelper->transformToDotSyntax($this->name);
     }
 

src/Kris/LaravelFormBuilder/FormHelper.php

@@ -456,7 +456,7 @@ public function appendMessagesWithPrefix(MessageBag $messageBag, $prefix, array
      */
     public function transformToDotSyntax($string)
     {
-        return str_replace(['.', '[]', '[', ']'], ['_', '', '.', ''], $string);
+        return str_replace(['.', '[]', '[', ']'], ['_', '', '.', ''], $string ?? '');
     }
 
     /**

tests/FormBuilderTestCase.php

@@ -65,7 +65,7 @@ public function buildForm()
 
     public function alterFieldValues(array &$values)
     {
-        $values['body'] = strtoupper($values['body']);
+        $values['body'] = strtoupper($values['body'] ?? '');
     }
 
     public function alterValid(Form $mainForm, &$isValid)