added constraints check for dbo deserialization

src/Utils/Dbo/LuDbo.php

             $doc = $parser->parse();
             $type = is_null($doc) ? null : $doc->getType();
 
+            $value = null;
             if (isset($json[$name])) {
                 $value = static::deserializeValue($json[$name], $type);
                 $property->setAccessible(true);
                 $property->setValue($dbo, $value);
-                
-                if ($doc->isNotNull() && is_null($value)) {
-                    throw new LuDboConstraintException("Field '" . $name . "' can not be null");
-                }
+            }
 
-                if (!is_null($doc) && !is_null($value)) {
-                    foreach ($doc->getConstraints() as $constraint) {
-                        call_user_func_array([$value, $constraint->getMethod()], $constraint->getArguments());
-                    }
+            if ($doc->isNotNull() && is_null($value)) {
+                throw new LuDboConstraintException("Field '" . $name . "' can not be null");
+            }
+
+            if (!is_null($doc) && !is_null($value)) {
+                foreach ($doc->getConstraints() as $constraint) {
+                    call_user_func_array([$value, $constraint->getMethod()], $constraint->getArguments());
                 }
             }
         }