CID 339035 (#1 of 1): Explicit null dereferenced (FORWARD_NULL)

signeedsfree doesn't correctly track whether sig.signature needs to be freed.

lib/dns/dnssec.c:

1054failure:
    	11. Condition dynbuf != NULL, taking false branch.
1055        if (dynbuf != NULL) {
1056                isc_buffer_free(&dynbuf);
1057        }
    	12. Condition signeedsfree, taking true branch.
1058        if (signeedsfree) {
    	
CID 339035 (#1 of 1): Explicit null dereferenced (FORWARD_NULL)
13. var_deref_model: Passing null pointer sig.signature to isc__mem_put, which dereferences it. [show details]
1059                isc_mem_put(mctx, sig.signature, sig.siglen);
1060        }
1061        if (ctx != NULL) {
1062                dst_context_destroy(&ctx);
1063        }