Fix nanmedian validation

[sahilphad07-sudo]

nanmedian did not correctly validate non-finite scalar and vector dimension arguments. This change adds validation for non-finite dimensions and regression tests for both cases.

Before

octave:1> nanmedian (ones (3), Inf)
ans =

   1   1   1
   1   1   1
   1   1   1

octave:2> nanmedian (ones (3), [1 Inf])
ans =

   1   1   1

Both calls returned results instead of raising dimension-validation errors.

After

octave:1> nanmedian (ones (3), Inf)
error: nanmedian: DIM must be a positive integer.

octave:2> nanmedian (ones (3), [1 Inf])
error: nanmedian: VECDIM must be a vector of positive integers.

MATLAB Behavior

>> nanmedian (ones (3), Inf)
Error using prctile
Dimension argument must be a positive integer scalar, a vector of unique positive integers, or 'all'.

>> nanmedian (ones (3), [1 Inf])
Error using prctile
Dimension argument must be a positive integer scalar, a vector of unique positive integers, or 'all'.

MATLAB rejects both invalid dimension arguments, consistent with the validation added in this change.

Regression Tests Added

• Non-finite scalar dimension (Inf).
• Non-finite dimension within a vector ([1 Inf]).

Test Results

• 24 out of 24 nanmedian BISTs pass.