Fix a crash in compile_to_object function

[Rainer Orth]

Hi Libor,

> I noticed it from the testsuite results (crash dump generated) for gdb
> 8.3. Although it is not implemented for Solaris, it should not crash, which
> is the reason why I sent a patch that resolves a nullptr dereference. The
> patched gdb prints an error message (instead of crashing) and the user can
> continue with debugging. I agree with you that there many more pressing
> issues that needs to be resolved first.

that explains why I'm not seeing this in my gdb builds: I use a
32-bit-default gcc 9.1 to build a 64-bit gdb, so there's no matching
libcc1.so around and the affected tests are UNTESTED.  Fully agreed that
there should be no crashes even for unsupported features, of course.

I'll leave the actual review to the responsible maintainers.

	Rainer

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Rainer Orth, Center for Biotechnology, Bielefeld University