Don't do mempool lookups for "mempool" command without a filter

src/main.cpp

@@ -4994,11 +4994,12 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         vector<CInv> vInv;
         BOOST_FOREACH(uint256& hash, vtxid) {
             CInv inv(MSG_TX, hash);
+            if (pfrom->pfilter) {
                 CTransaction tx;
                 bool fInMemPool = mempool.lookup(hash, tx);
                 if (!fInMemPool) continue; // another thread removed since queryHashes, maybe...
-            if ((pfrom->pfilter && pfrom->pfilter->IsRelevantAndUpdate(tx)) ||
-               (!pfrom->pfilter))
+                if (!pfrom->pfilter->IsRelevantAndUpdate(tx)) continue;
+            }
             vInv.push_back(inv);
             if (vInv.size() == MAX_INV_SZ) {
                 pfrom->PushMessage("inv", vInv);