fix: range should accept 0 as valid value

[kmorales13]

In the function setRange, range values of 0 will be treated as falsy.
These should be valid, for example, if we want to show only the first slide.

Input:

slides: [1,2,3],
...
range: {
  min: 0,
  max: 0,
}

Output:

minIdx: 0,
maxIdx: 2,

Expected:

minIdx: 0,
maxIdx: 0,