dnsapi: Fix some potential infinite loops because of an unsigned loop counter.

dlls/dnsapi/query.c

@@ -418,8 +418,7 @@ static DNS_STATUS dns_copy_rdata( ns_msg msg, const ns_rr *rr, DNS_RECORDA *r, W
             r->Data.TXT.pStringArray[i] = dns_str_from_rdata( pos );
             if (!r->Data.TXT.pStringArray[i])
             {
-                for (--i; i >= 0; i--)
-                    dns_free( r->Data.TXT.pStringArray[i] );
+                while (i > 0) dns_free( r->Data.TXT.pStringArray[--i] );
                 return ERROR_NOT_ENOUGH_MEMORY;
             }
             i++;

dlls/dnsapi/record.c

@@ -443,8 +443,7 @@ PDNS_RECORD WINAPI DnsRecordCopyEx( PDNS_RECORD src, DNS_CHARSET in, DNS_CHARSET
 
             if (!dst->Data.TXT.pStringArray[i])
             {
-                for (--i; i >= 0; i--)
-                    dns_free( dst->Data.TXT.pStringArray[i] );
+                while (i > 0) dns_free( dst->Data.TXT.pStringArray[--i] );
                 goto error;
             }
         }