Allow empty include paths

[abakst]

Given main.c

int main() {
  assert(0);
  return 0;
}

and header.h:

void assert(int x);

and compile_commands.json derived from

clang -c -include header.h main.c

c2rust transpile compile_commands.json panics in TypedAstContext::include_path because the include path for header.h is None.

This PR fixes the panic by first checking if the root include is not None.

[abakst]

I would happily add a regression test, but I'm not sure exactly where to put it.

[kkysen]

I would happily add a regression test, but I'm not sure exactly where to put it.

Our testing infrastructure isn't very well setup to test custom compile commands, so I'm not sure this is easily testable, but I think it's simple enough to not need a test. Also, this seems to be in a cfg!(debug_assertions), so are you also encountering this error in a release build?

Otherwise it LGTM besides whatever rustfmt is complaining about.

[abakst]

I would happily add a regression test, but I'm not sure exactly where to put it.

Our testing infrastructure isn't very well setup to test custom compile commands, so I'm not sure this is easily testable, but I think it's simple enough to not need a test. Also, this seems to be in a cfg!(debug_assertions), so are you also encountering this error in a release build?

Otherwise it LGTM besides whatever rustfmt is complaining about.

No this was in a debug build. Thanks!

[abakst]

@kkysen apologies but do I re-trigger the CI actions so that I can merge?