Fix: linspace accepts integer divisions only + undefined variable bug

[CsatiZoltan]

I checked all the occurences of linspace using

grep -rn "linspace" ./

from the main directory of ImagePy. In all the cases when the third argument of linspace was float, I probed the given method in debugging mode and they indeed failed. After these corrections, the linspace issue is solved.

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The other change is for an undefined variable.