Fix bug #8101: tshark -2 -r fragments.pcap -R snmp -w out.pcap segmentation fault

When doing second pass tshark, packet data is read to cf->pd (and not already freed cf->wth buffer).
Writting files with two pass analysis never worked, buggy since introducing two pass analysis in r30076.

svn path=/trunk/; revision=47851

tshark.c

@@ -2943,7 +2943,7 @@ load_cap_file(capture_file *cf, char *save_file, int out_file_type,
              filter, so, if we're writing to a capture file, write
              this packet out. */
           if (pdh != NULL) {
-            if (!wtap_dump(pdh, &cf->phdr, wtap_buf_ptr(cf->wth), &err)) {
+            if (!wtap_dump(pdh, &cf->phdr, cf->pd, &err)) {
               /* Error writing to a capture file */
               switch (err) {