fix memory leak for protocol_copyPropertyList (#680)

* fix memory leak for protocol_copyPropertyList

Author: wolfcon

MJExtension.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name         = "MJExtension"
-  s.version      = "3.0.16"
+  s.version      = "3.0.17"
   s.ios.deployment_target = '8.0'
   s.osx.deployment_target = '10.8'
   s.summary      = "A fast and convenient conversion between JSON and model"

MJExtension/MJFoundation.m

@@ -61,6 +61,7 @@ + (BOOL)isFromNSObjectProtocolProperty:(NSString *)propertyName
             }
         }
         objectProtocolPropertyNames = [propertyNames copy];
+        free(propertyList);
     });
 
     return [objectProtocolPropertyNames containsObject:propertyName];