Only check connectedness in StarscreamWebSocket

This should hopefully be enough to prevent Starscream from silently
swallowing the continuation.

Sources/LighthouseWebSocket/Implementation/StarscreamWebSocket.swift

@@ -9,7 +9,7 @@ public final actor _StarscreamWebSocket: WebSocketProtocol, Starscream.WebSocket
     private var webSocket: Starscream.WebSocket
     private var connectHandlers: [(Result<Void, any Error>) -> Void] = []
     private var binaryMessageHandlers: [(Data) -> Void] = []
-    private var isSending: Bool = false
+    private var isConnected: Bool = false
 
     public init(url: URL) {
         webSocket = Starscream.WebSocket(request: URLRequest(url: url))
@@ -22,6 +22,7 @@ public final actor _StarscreamWebSocket: WebSocketProtocol, Starscream.WebSocket
             connectHandlers.append(continuation.resume(with:))
             webSocket.connect()
         }
+        isConnected = true
     }
 
     public func onBinary(_ handler: @escaping (Data) -> Void) throws {
@@ -56,18 +57,12 @@ public final actor _StarscreamWebSocket: WebSocketProtocol, Starscream.WebSocket
     }
 
     public func send(_ data: Data) async throws {
-        // We have to serialize all message sends, for which we need
-        // a flag (actor isolation is not sufficient to due reentrancy).
-        while isSending {
-            try await Task.sleep(for: .milliseconds(2))
-        }
+        guard isConnected else { throw WebSocketError.notConnectedYet }
 
-        isSending = true
         log.trace("Sending binary message")
         await withCheckedContinuation { continuation in
             webSocket.write(data: data, completion: continuation.resume)
         }
-        isSending = false
     }
 }
 #endif