Show error when trader id can't be found in Traders enum

Exit early when sending messages from trader if no trader supplied

project/src/helpers/TraderHelper.ts

@@ -396,6 +396,13 @@ export class TraderHelper
     {
         const keys = Object.keys(Traders).filter(x => Traders[x] === traderId);
 
-        return keys.length > 0 ? keys[0] as Traders : null;
+        if (keys.length === 0)
+        {
+            this.logger.error(`Unable to find trader: ${traderId} in Traders enum`);
+
+            return null;
+        }
+
+        return keys[0] as Traders;
     }
 }

project/src/services/MailSendService.ts

@@ -43,6 +43,13 @@ export class MailSendService
      */
     public sendDirectNpcMessageToPlayer(playerId: string, sender: Traders, messageType: MessageType, message: string, items: Item[] = [], maxStorageTimeSeconds = null): void
     {
+        if (!sender)
+        {
+            this.logger.error(`Unable to send message type: ${messageType} to player: ${playerId}, provided trader enum was null`);
+
+            return;
+        }
+
         const details: ISendMessageDetails = {
             recipientId: playerId,
             sender: messageType,
@@ -72,6 +79,13 @@ export class MailSendService
      */
     public sendLocalisedNpcMessageToPlayer(playerId: string, sender: Traders, messageType: MessageType, messageLocaleId: string, items: Item[] = [], maxStorageTimeSeconds = null): void
     {
+        if (!sender)
+        {
+            this.logger.error(`Unable to send message type: ${messageType} to player: ${playerId}, provided trader enum was null`);
+
+            return;
+        }
+
         const details: ISendMessageDetails = {
             recipientId: playerId,
             sender: messageType,