Clam 1651 #2: Fix leak loading malformed PDB database

[ragusaa]

This addresses the pdb memory leaks in the ticket. Will do separate PRs for other issues that are not in the same files.

Fixes: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=43849
Fixes: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=44115

[val-ms]

Looks like this was changed (slightly differently) in https://github.com/Cisco-Talos/clamav/pull/530/files#diff-c2d7ebcb1295f163964c14d878838c83e69061189c318f01909d34dd5a383a98L427-L466

This version:

• isn't clang-formatted
• doesn't use the VERIFY_POINTER macros
• does have better error handling for the parse_regex() call.

How do you want to proceed? Do you want to merge these two PR's? Do you want to take the improvements from this one and put them in #530? Or?

[val-ms]

From offline conversation: because of the overlap with #530, the plan is to fix-up that one and merge that first -- then rebase this and fix the merge conflicts, and then merge this. So until #530 lands, this one is blocked.

[ragusaa]

The updates to PR-530 appear to have removed the merge conflicts, because when I did a 'git pull', there was nothing to merge. I clang-formatted, so I am ready for re-review.

[val-ms]

Everything checks out. This was a little difficult to verify because the 2 PoC's for this were mixed in with 4 PoC's for related issues. But manual testing confirmed all is well with this PR.