checking current attribute value for nullable before comparing

Author: golubkovden

src/Illuminate/Database/Eloquent/Concerns/HasAttributes.php

@@ -986,6 +986,12 @@ protected function originalIsEquivalent($key, $current)
             return true;
         }
 
+        // When check rich this check and current attribute value not equals with original, we should skip next steps
+        // if current is null
+        if (is_null($current)) {
+            return false;
+        }
+
         if ($this->isDateAttribute($key)) {
             return $this->fromDateTime($current) === $this->fromDateTime($original);
         }

tests/Database/DatabaseEloquentModelTest.php

@@ -74,18 +74,21 @@ public function testDirtyOnCastOrDateAttributes(){
         $model->foo = 1;
         $model->bar = '2017-03-18';
         $model->dateAttribute = '2017-03-18';
+        $model->datetimeAttribute = '2017-03-23 22:17:00';
         $model->syncOriginal();
 
+        $model->boolAttribute = true;
         $model->foo = true;
         $model->bar = '2017-03-18 00:00:00';
-        $model->boolAttribute = true;
         $model->dateAttribute = '2017-03-18 00:00:00';
+        $model->datetimeAttribute = null;
 
         $this->assertTrue($model->isDirty());
         $this->assertTrue($model->isDirty('foo'));
         $this->assertTrue($model->isDirty('bar'));
         $this->assertFalse($model->isDirty('boolAttribute'));
         $this->assertFalse($model->isDirty('dateAttribute'));
+        $this->assertTrue($model->isDirty('datetimeAttribute'));
     }
 
     public function testCleanAttributes()