Fix infinite rpc.gascap on eth_estimateGas (#1292)

* Fix infinite rpc.gascap on eth_estimateGas

* use `gasCap.Sign() > 0` instead of `gasCap.Uint64() != 0`

cmd/rpcdaemon/commands/eth_call.go

@@ -106,7 +106,7 @@ func (api *APIImpl) DoEstimateGas(ctx context.Context, args ethapi.CallArgs, blo
 		}
 	}
 	// Recap the highest gas allowance with specified gascap.
-	if gasCap != nil && hi > gasCap.Uint64() {
+	if gasCap != nil && gasCap.Sign() > 0 && hi > gasCap.Uint64() {
 		log.Warn("Caller gas above allowance, capping", "requested", hi, "cap", gasCap)
 		hi = gasCap.Uint64()
 	}