[Matlab] Fix default threshold value when displaying phase info

At some point (after version 2014b), Matlab started passing an additional
argument to 'display', which broke the logic for setting the default
threshold. This caused all composition data to be excluded from the report shown
by typing the name of the phase object.

interfaces/matlab/toolbox/@ThermoPhase/display.m

@@ -1,5 +1,5 @@
 function display(self, threshold)
-if nargin < 2
+if nargin < 2 || ~isnumeric(threshold)
     threshold = 1e-14;
 end
 phase_get(thermo_hndl(self), 15, 1, threshold);