Prevent sell and buy offers to be canceled by anybody (#9)

- Prevent sell and buy offers to be canceled by anybody

src/cc/CCtx.cpp

@@ -175,7 +175,7 @@ std::string FinalizeCCTx(uint64_t CCmask,struct CCcontract_info *cp,CMutableTran
                 else
                 {
                     fprintf(stderr,"CC signing error: vini.%d has unknown CC address.(%s)\n",i,destaddr);
-                    continue;
+                    return("");
                 }
                 uint256 sighash = SignatureHash(CCPubKey(cond), mtx, i, SIGHASH_ALL, utxovalues[i],consensusBranchId, &txdata);
                 if ( cc_signTreeSecp256k1Msg32(cond,privkey,sighash.begin()) != 0 )
@@ -192,6 +192,7 @@ std::string FinalizeCCTx(uint64_t CCmask,struct CCcontract_info *cp,CMutableTran
                 else
                 {
                     fprintf(stderr,"vini.%d has CC signing error address.(%s)\n",i,destaddr);
+                    return("");
                 }
             }
         } else fprintf(stderr,"FinalizeCCTx couldnt find %s\n",mtx.vin[i].prevout.hash.ToString().c_str());