[tz] source code question regarding localtime.c

[Alois Treindl]

In localtime.c, function localsub() are these three lines of code:

1295    icycles = tcycles;
1296    if (tcycles - icycles >= 1 || icycles - tcycles >=  1)
1297      return NULL;

I do not understand the reason why lines 1296 and 1297 exist.
icycles and tcycles are equal.
Their difference is always zero. Why test for it being not zero?