Add error handler for GNUstep apps missing their fonts

**GNUstep gui programs failing**

**To Reproduce**
Steps to reproduce the behavior:

2 examples

sudo pkg install gnustep systempreferences
openapp SystemPreferences

or

sudo pkg install gmines
open startvalume.
drill down to /usr/local/GNUstep/System//Applications
click on gmines

**Expected behavior**
I expect a gui to open displaying the gnustep sysm preferences
or
I expect to play gmines
__
**Screenshots**

**Version (please complete the following information):**
- installed system
- FreeBSD version FreeBSD 12.2-RELEASE r366954 GENERIC
- helloSystem build (`cat /.url`): https://github.com/helloSystem/ISO/releases/tag/r0.5.0
- Running in a virtual machine: no

**Computer (please complete the following information):**
- Device: ASUS ZenBook UX305UA

**Additional context**
the compiler is working, and my programs that use command line or X11, or SDL2 are working.
But programs using the native AppKit for their gui all fail. Example:

sudo pkg install gnustep systempreferences
openapp SystemPreferences

fails with pages and pages of:
2021-07-06 23:49:37.960 SystemPreferences[14543:101571] The font specified for NSFont, Helvetica, can't be found.

Also, the Helvetica font seems to be installed:
darko@sudanna /usr/local/GNUstep/System/Library/Fonts/Helvetica.nfont $ ls
FontInfo.plist n019004l.pfb n019024l.afm n019043l.pfm n019063l.pfb
n019003l.afm n019004l.pfm n019024l.pfb n019044l.afm n019063l.pfm
n019003l.pfb n019023l.afm n019024l.pfm n019044l.pfb n019064l.afm
n019003l.pfm n019023l.pfb n019043l.afm n019044l.pfm n019064l.pfb
n019004l.afm n019023l.pfm n019043l.pfb n019063l.afm n019064l.pfm