Fix prevent issue - Unsigned compared against 0

Fix prevent issue - Unsigned compared against 0

- Since t/step can be negative number, min = static_cast<int>(t/step); and
if( min < 0) might cause unexpected behavior.
- Introduce new float tLocation variable instead of direct assigning
t/step to unsigned min variable.

<Prevent message>
CID 436228 (#1 of 1): Unsigned compared against 0 (NO_EFFECT)
unsigned_compare: This less-than-zero comparison of an unsigned value is never true. min < 0U.
 95        if( min < 0)

Change-Id: Id1be5aaf7a03f04f9cf61b1ad947f08bacb78563