[dispatcher] fix chaining and freeing of probing packs

Some probing packs may be freed before ending circulating the list (if the prob sending fails), so we need to take care of the linking.

modules/dispatcher/dispatch.c

@@ -2762,6 +2762,7 @@ void ds_check_timer(unsigned int ticks, void* param)
 						pack_last->next = pack;
 						pack_last = pack;
 					}
+					pack->next = NULL;
 
 				}
 			}
@@ -2770,7 +2771,9 @@ void ds_check_timer(unsigned int ticks, void* param)
 		lock_stop_read( partition->lock );
 
 		/* now send all the probs, outside the lock */
-		for( pack = pack_head ; pack ; pack=pack->next ) {
+		for( pack = pack_head ; pack ; pack=pack_last ) {
+
+			pack_last = pack->next;
 
 			/* Execute the Dialog using the "request"-Method of the
 			 * TM-Module.*/