butc: avoid freeing uninitialized pointer in writeDbDump()

butc: avoid freeing uninitialized pointer in writeDbDump()

In error conditions, charList could be freed before it is initialized.
Move the initialization up to before the error checks.

Change-Id: I678f40552590e238f494507f7410233cdbb949ac
Found-by: clang static analyzer
Reviewed-on: http://gerrit.openafs.org/5167
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Simon Wilkinson <sxw@inf.ed.ac.uk>
Reviewed-by: Derrick Brashear <shadow@dementia.org>