setting a default for non-existent property

[Ben Abbott]

I accidently set a default for a non-existent property and discovered  
I had to quit octave to recover.

For example ...

octave:5> set (0, "defaultfigure_bad_property", 0)
octave:6> figure
error: set: unknown property "_bad_property"
error: error setting default property _bad_property
error: __go_figure__: failed to create figure handle
error: called from:
error:   /Users/bpabbott/Development/mercurial/local_clone/scripts/ 
plot/figure.m at line 67, column 9

I assume the same is true for all defaults (text, axes, figure, etc).

Can someone with better c/c++ skills take a look at fixing this?

Ben