fix: guard all ws.send() calls with readyState check to prevent server crashes (#3936)

## Description:

Several ws.send() calls in GameServer.ts were missing WebSocket.OPEN
readyState guards. This can lead to server crashes if a client
disconnects precisely between a check and the send. Added guards to
prestart, kickClient, and handleSynchronization.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
## Please put your Discord username so you can be contacted if a bug or
regression is found:

barfires

Co-authored-by: 22314621 <22314621@student.ciu.edu.tr>

src/server/GameServer.ts

@@ -672,7 +672,9 @@ export class GameServer {
         clientID: c.clientID,
         persistentID: c.persistentID,
       });
-      c.ws.send(msg);
+      if (c.ws.readyState === WebSocket.OPEN) {
+        c.ws.send(msg);
+      }
     });
   }
 
@@ -999,13 +1001,15 @@ export class GameServer {
         persistentID: client.persistentID,
         reasonKey,
       });
-      client.ws.send(
-        JSON.stringify({
-          type: "error",
-          error: reasonKey,
-        } satisfies ServerErrorMessage),
-      );
-      client.ws.close(1000, reasonKey);
+      if (client.ws.readyState === WebSocket.OPEN) {
+        client.ws.send(
+          JSON.stringify({
+            type: "error",
+            error: reasonKey,
+          } satisfies ServerErrorMessage),
+        );
+        client.ws.close(1000, reasonKey);
+      }
       this.activeClients = this.activeClients.filter(
         (c) => c.clientID !== clientID,
       );
@@ -1137,7 +1141,9 @@ export class GameServer {
         clientID: c.clientID,
         persistentID: c.persistentID,
       });
-      c.ws.send(desyncMsg);
+      if (c.ws.readyState === WebSocket.OPEN) {
+        c.ws.send(desyncMsg);
+      }
     }
   }