Remove warnings from `herrorbar`
Remove warnings from `herrorbar`

This produces warnings in Octave (and Mlint warnings in MATLAB).
Just fix those to avoid cluttering the test output.

LJeub/matlab2tikz,RPeschke/matlab2tikz,matlab2tikz/matlab2tikz,egeerardyn/matlab2tikz,egeerardyn/matlab2tikz,nidrosianDeath/matlab2tikz,matlab2tikz/matlab2tikz,PeterPablo/matlab2tikz,miscco/matlab2tikz