libctf: fix uninitialized variable in symbol serialization error handling

libctf: fix uninitialized variable in symbol serialization error handling

We declare a variable to hold errors at two scopes, and then initialize
the inner one and jump to a scope where only the outer one is in scope.

The consequences are minor: only the version of the error message
printed in the debugging stream is impacted.

libctf/ChangeLog
2021-01-27  Nick Alcock  <nick.alcock@oracle.com>

	* ctf-create.c (ctf_serialize): Fix shadowing.