New Issue Checklist

• I have read and understood the CONTRIBUTING guide
• I have read the Documentation
• I have searched for a similar issue in the project and found none

Issue Info

Info	Value
Platform Name	e.g. ios / tvos
Platform Version	e.g. 8.0
SDWebImage Version	e.g. 3.7.6
Integration Method	e.g. carthage / cocoapods / manually
Xcode Version	e.g. Xcode 7.3
Repro rate	e.g. all the time (100%) / sometimes x% / only once
Repro with our demo prj	e.g. does it happen with our demo project?
Demo project link	e.g. link to a demo project that highlights the issue

Issue Description and Steps

Please fill in the detailed description of the issue (full output of any stack trace, compiler error, ...) and the steps to reproduce the issue.