libctf: fix uninitialized variables in testsuite

Just because a path is an error path doesn't mean the program terminates
there if you don't ask it to.  And we don't want to -- but that means
we need to initialize the variables that are missed if an error happens to
*something*.  Type ID 0 (unimplemented) will do: it'll induce further
ECTF_BADID errors, but that's no bad thing.

libctf/ChangeLog:

	* testsuite/libctf-writable/libctf-errors.c: Initialize variables.