fix: cy-c>cy+c will make poly be screwd in function "getPoly_core"

[sevenHsu]

if cp_section[-1]==[0,0], make last cy-c>cy+c. The final poly will be screwed

[daniellovera]

if cp_section[-1]==[0,0], make last cy-c>cy+c. The final poly will be screwed

I know this is years later, but any chance you can provide more context on what you meant by saying the final poly will be screwed? I've been using polys instead of the boxes so I'd like to make sure they are accurate.