Fix crash due to use after free or double-free

... bug introduced in commit 29a35642.

strListMerge() doesn't realloc the strings in the list, so we don't want to
free the strings in this list here.

This is likely the cause of the crash Keyop eluded to in #synchronet.

src/sbbs3/un_qwk.cpp

@@ -139,7 +139,7 @@ bool sbbs_t::unpack_qwk(char *packet,uint hubnum)
 	msg_filters.twit_list = list_of_twits(&cfg);
 	str_list_t ip_silent_list = trashcan_list(&cfg, "ip-silent");
 	strListMerge(&msg_filters.ip_can, ip_silent_list);
-	strListFree(&ip_silent_list);
+	free(ip_silent_list);
 
 	for(l=QWK_BLOCK_LEN;l<size;l+=blocks*QWK_BLOCK_LEN) {
 		if(terminated) {

src/sbbs3/un_rep.cpp

@@ -175,7 +175,7 @@ bool sbbs_t::unpack_rep(char* repfile)
 	msg_filters.twit_list = list_of_twits(&cfg);
 	str_list_t ip_silent_list = trashcan_list(&cfg, "ip-silent");
 	strListMerge(&msg_filters.ip_can, ip_silent_list);
-	strListFree(&ip_silent_list);
+	free(ip_silent_list);
 
 	now=time(NULL);
 	for(l=QWK_BLOCK_LEN;l<size;l+=blocks*QWK_BLOCK_LEN) {