Fix crash with nil messages

prog2/slotV2.lua

@@ -1,40 +1,47 @@
 --slot2
 rednet.open("back")
 
+
 local function interactWithCard(userUUID, mode, money)
-    if mode == "updateBalance" then
-        rednet.broadcast({
-            uuid = userUUID,
-            amount = money,
-            type = "set"
-        }, "machineBalanceModifier")
-    end
+if mode == "updateBalance" then
+  rednet.broadcast({
+    uuid = userUUID,
+    amount = money,
+    type = "set"
+  }, "machineBalanceModifier")
+  end
 
-    if mode == "getBalance" then
-        local _, _, cardUUID = os.pullEvent("nfc_data")
-        rednet.broadcast({
-            card = cardUUID
-        }, "getAccountData")
+  if mode == "getBalance" then
+    local _, _, cardUUID = os.pullEvent("nfc_data")
+    rednet.broadcast({
+      card = cardUUID
+    }, "getAccountData")
 
-        while true do
-            local id, message = rednet.receive("server_response", 10)
-            if not id then
-                print("the server is down")
-                print("please ping @minecartchris")
-                sleep(30)
-                --shell.run("reboot")
-            end
-            if message.type == "account_data" and message.cardId == cardUUID then
-                local money = message.balance
-                local playerUUID = message.uuid
-                local username = message.username
-                return money, playerUUID, username
-            end
+    while true do
+      local id, message = rednet.receive("server_response", 10)
+      if not id then
+        print("the server is down")
+        print("please ping @minecartchris")
+        sleep(30)
+        --shell.run("reboot")
+      end
+      if not message then
+        print("WTF!? I got a rednet message with no data!?")
+        print("Rebooting...")
+        sleep(5)
+      end
+      if message.type == "account_data" and message.cardId == cardUUID then
+        local money = message.balance
+        local playerUUID = message.uuid
+        local username = message.username
+        return money, playerUUID, username
+      end
 
-        end
     end
+  end
 end
 
+
 os.pullEvent= function(...)
     while true do
         local t = table.pack(os.pullEventRaw(...))
@@ -163,4 +170,4 @@ end
 shell.execute("clear")
 while true do
   run()
-end
+end