bug#11541: 24.0.97; Crash when visiting file on OS X 10.7.3

[C. Florian Ebeling]

> This might be a slower way to find the culprit, but I think it is a
> lot more sure to give good results.

This is what a healthy and the crashing call produce with font_spec and fdesc 
being printed:

Breakpoint 2, ns_findfonts (font_spec=4338015181, isMatch=0 '\000') at 
nsfont.m:496
496         Lisp_Object tem, list = Qnil;
#<font-spec ns nil Monaco nil iso10646-1 nil nil nil nil nil nil nil ((:script 
. symbol))>

Breakpoint 3, ns_findfonts (font_spec=4338015181, isMatch=0 '\000') at 
nsfont.m:529
529         if (!FONT_SPEC_P (font_spec))
#<font-spec ns nil Monaco nil iso10646-1 nil nil nil nil nil nil nil ((:script 
. symbol))>

Breakpoint 2, ns_findfonts (font_spec=4338015181, isMatch=0 '\000') at 
nsfont.m:496
496         Lisp_Object tem, list = Qnil;
#<font-spec ns apple nil nil iso10646-1 nil nil nil nil nil nil nil ((:script . 
symbol))>

Breakpoint 3, ns_findfonts (font_spec=4338015181, isMatch=0 '\000') at 
nsfont.m:529
529         if (!FONT_SPEC_P (font_spec))
#<font-spec ns apple nil nil iso10646-1 nil nil nil nil nil nil nil ((:script . 
symbol))>

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0x0000000000000000
0x00007fff8966d3c2 in CFStringGetLength ()

(gdb) i b
Num Type           Disp Enb Address            What
--- snip ---
2   breakpoint     keep y   0x00000001001a0fb5 in ns_findfonts at nsfont.m:496
        breakpoint already hit 7 times
        pp font_spec
        continue
3   breakpoint     keep y   0x00000001001a11ca in ns_findfonts at nsfont.m:529
        breakpoint already hit 7 times
        pp font_spec
        continue

I can't really tell which font_spec is acceptable, and which not, though.

The crashing one has a third element of nil, is that ok or not?