Fix narrowing error/warning in canny
Fix narrowing error/warning in canny

arrayfire/arrayfire,umar456/arrayfire,arrayfire/arrayfire,umar456/arrayfire,munnybearz/arrayfire,munnybearz/arrayfire,9prady9/arrayfire,arrayfire/arrayfire,9prady9/arrayfire,9prady9/arrayfire,munnybearz/arrayfire,umar456/arrayfire,umar456/arrayfire,arrayfire/arrayfire,9prady9/arrayfire