Fix memory leaks and add bounds checks in packet/drop handling

GetNewDrop() allocated newdrop up front but returned NULL without
freeing it on every rejection path (failed drop-rate check, missing
drop table, unknown item type, etc.), leaking on every non-drop roll.
Free it on all early-return paths, and only assign a clientid once a
drop is actually going to be returned.

CPacket::AddByte/Word/DWord/QWord/Float now bounds-check against the
buffer before writing, preventing an overflow if a packet is built
past its allocated size.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Src/World Server/ServerFunctions.cpp

@@ -133,10 +133,9 @@ CDrop* CWorldServer::GetNewDrop( CMonster* thismon )
     CMDrops* thisdrop = NULL;
     CMDrops* testdrop = NULL;
 
-    newdrop->clientid = GetNewClientID( );
     newdrop->posMap = thismon->Position->Map;
     newdrop->pos = RandInCircle( thismon->Position->current, 3 );
-    //newdrop->droptime = time(NULL);
+    newdrop->droptime = time(NULL);
     newdrop->owner = thismon->MonsterDrop->firsthit;
     newdrop->thisparty = thismon->thisparty;
     ClearItem(newdrop->item);
@@ -158,6 +157,7 @@ CDrop* CWorldServer::GetNewDrop( CMonster* thismon )
     {
         if( thisclient->Session->codedebug )
             SendPM(thisclient, "Drop rate check failed with %i. No drop this time",droprand);
+        delete newdrop;
         return NULL; // no drop here. not this time anyway.
     }
 
@@ -177,6 +177,7 @@ CDrop* CWorldServer::GetNewDrop( CMonster* thismon )
         {
            SendPM(thisclient, "Zuly drop selected " );
         }
+        newdrop->clientid = GetNewClientID( );
         return  newdrop;
     }
     //now check for item drops
@@ -194,7 +195,7 @@ CDrop* CWorldServer::GetNewDrop( CMonster* thismon )
             for(i=0;i<GServer->MDropList.size();i++)
             {
                 testdrop =  GServer->MDropList.at(i);
-                if(testdrop == NULL) return NULL;
+                if(testdrop == NULL) { delete newdrop; return NULL; }
                 if(testdrop->Dropid == thismon->Position->Map)
                 {
                     thisdrop = testdrop;
@@ -211,7 +212,7 @@ CDrop* CWorldServer::GetNewDrop( CMonster* thismon )
             for(i=0;i<GServer->MDropList.size();i++)
             {
                 testdrop =  GServer->MDropList.at(i);
-                if(testdrop == NULL) return NULL;
+                if(testdrop == NULL) { delete newdrop; return NULL; }
                 if(testdrop->Dropid == thismon->thisnpc->dropid)
                 {
                     thisdrop = testdrop;
@@ -225,6 +226,7 @@ CDrop* CWorldServer::GetNewDrop( CMonster* thismon )
         if(thisdrop == NULL)
         {
             Log(MSG_WARNING, "Thisdrop is NULL [getdrop]" );
+            delete newdrop;
             return NULL;
         }
         newdrop->type = 2; //Item
@@ -250,6 +252,7 @@ CDrop* CWorldServer::GetNewDrop( CMonster* thismon )
         if(thisdrop->item[itemindex] == 0)
         {
             Log(MSG_DEBUG, "item at itemindex %i does not exist",itemindex );
+            delete newdrop;
             return NULL; //no item listed for this dropid
         }
         //ok we found an item. Now we process it.
@@ -296,6 +299,7 @@ CDrop* CWorldServer::GetNewDrop( CMonster* thismon )
                 break;
             default:
                 Log(MSG_DEBUG, "itemtype %i does not exist",newdrop->item.itemtype );
+                delete newdrop;
                 return NULL;
                 break;
         }
@@ -399,9 +403,11 @@ CDrop* CWorldServer::GetNewDrop( CMonster* thismon )
         {
            SendPM(thisclient, "Dropped item type: %i ID: %i count %i", newdrop->item.itemtype, newdrop->item.itemnum,newdrop->item.count);
         }
+        newdrop->clientid = GetNewClientID( );
         return newdrop;
 
     }
+    delete newdrop;
     return NULL;
     // did not qualify to drop anything this time
 }