Add check for invalid house ID

scripts/server/house.js

@@ -774,6 +774,10 @@ function createHouse(description, entrancePosition, exitPosition, entrancePickup
 // ===========================================================================
 
 function getHouseDataFromDatabaseId(databaseId) {
+	if (databaseId <= 0) {
+		return false;
+	}
+
 	let matchingHouses = getServerData().houses.filter(b => b.databaseId == databaseId)
 	if (matchingHouses.length == 1) {
 		return matchingHouses[0];
@@ -1431,6 +1435,10 @@ function buyHouseCommand(command, params, client) {
  * @return {HouseData} The house's data (class instance)
  */
 function getHouseData(houseId) {
+	if (houseId == -1) {
+		return false;
+	}
+
 	if (typeof getServerData().houses[houseId] != "undefined") {
 		return getServerData().houses[houseId];
 	}