Fix condition to eliminate TID overflow issue

[martyy665]

Fix tid overflow issue when tid is zero.

These two snippets are NOT the same - the difference appears when the numeric variable reaches zero (i.e. overflows):

if not tid :
    ...

if tid is None :
    ....

Reference:
#2173

[janiversen]

You are correct they are not the same. yours test for none and zero.

[janiversen]

Thanks.