Corrected single-y bar width bug
Corrected single-y bar width bug

Corrected a bug where the bar width calculation threw an error
when dealing with a single bar object (i.e. only one y dataset
passed as input to boxplot2) in HG2 versions of Matlab (2016b+).

In addition to not plotting the proper results, this bug resulted
in the hidden figure being left open, stealing focus from any future
plotting commands.

Corrected the bar width calculation to properly deal with single-
boxplot input.  I also added a try-catch loop around the code that
uses the hidden figure, ensuring that the hidden figure is closed
even if that code hits an unexpected error.

kakearney/boxplot2-pkg