Fix app crash on viewing exam statistics after completing exam
Fix app crash on viewing exam statistics after completing exam

- From exam statistics we will unlock next content if attempt percentage is greater than
pass percentage.
- To unlock next content we will change isLocked status to true.
- Issue is write operations on Realm object should be wrapped within Realm.write or else app will crash

testpress/ios-app,testpress/ios-app,testpress/ios-app,testpress/ios-app