Improve handling on images without QR code

[TheWindRider]

This spins off issue #19
After testing with several images without QR code, I've seen 3 different outcomes (there might be more I have not discovered). I'm new to this repo and may not able to tackle these immediately.
Further divide-and-conquer might be useful.

1. program finished with QR code output by mistake
   
2. program seemed to get stucked until keyboard interruption
   
3. program exited with error
   

[lavi061997]

@Griffintaur I would like to contribute and solve this issue

[Griffintaur]

@lavi061997 that would be great .I highly appreciate your contribution.
Lets break into three different issues and solve them iteratively.