代码优化 review by 阿瑟

@@ -255,7 +255,6 @@ export default function community(platform) {
 								hideNavBar={false}
 								component={SystemMessageContainer}
 								initial={false}
-								onBack={this.onBack}
 								getSceneStyle={(props) => {
 									return this.navPushStyle(props);
 								}}
@@ -299,7 +298,6 @@ export default function community(platform) {
 								hideNavBar={false}
 								component={SubjectPostContainer}
 								initial={false}
-								onBack={this.onBack}
 								rightButtonImage={require('./images/posting/share.png')}
 								onRight={this.subjectPostOnRight}
 								getSid={()=>{