Prevent sending interop to finished session controllers.

src/Tgstation.Server.Host/Components/Watchdog/SessionController.cs

@@ -447,6 +447,15 @@ namespace Tgstation.Server.Host.Components.Watchdog
 
 		async Task<string> SendCommand(string command, ushort? overridePort, CancellationToken cancellationToken)
 		{
+			if (Lifetime.IsCompleted)
+			{
+				logger.LogWarning(
+					"Attempted to send a command to an inactive SessionController{1}: {0}",
+					command,
+					overridePort.HasValue ? $" (Override port: {overridePort.Value})" : String.Empty);
+				return null;
+			}
+
 			try
 			{
 				var commandString = String.Format(CultureInfo.InvariantCulture,

src/Tgstation.Server.Host/Components/Watchdog/WatchdogBase.cs

@@ -426,6 +426,9 @@ namespace Tgstation.Server.Host.Components.Watchdog
 		/// <inheritdoc />
 		public async Task<bool> HandleEvent(EventType eventType, IEnumerable<string> parameters, CancellationToken cancellationToken)
 		{
+			if (!Running)
+				return true;
+
 			string results;
 			using (await SemaphoreSlimContext.Lock(Semaphore, cancellationToken).ConfigureAwait(false))
 			{