Bug: Internal server error when trying to remove non existing scene

[malliaridis]

Description

When trying to remove a scene that does not exist or when trying to remove a scene twice an internal server error is thrown because of a null pointer exception.

Environment details

Streamlabs OBS Version: 1.4.0
Operating System: Windows

Steps to reproduce the bug

1. Connect to Streamlabs OBS
2. Send following request (SceneService.removeScene):

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "removeScene",
  "params": {
    "resource": "ScenesService",
    "args": ["scene_id_that_does_not_exist"]
  }
}

3. See response:

{"id":8,"jsonrpc":"2.0","error":{"code":-32000,"message":"INTERNAL_SERVER_ERROR Cannot read property 'getModel' of null TypeError: Cannot read property 'getModel' of null
    at ScenesService.removeScene (https://slobs-cdn.streamlabs.com/bundles/renderer.js:1:4384089)
    at Proxy.<anonymous> (https://slobs-cdn.streamlabs.com/bundles/renderer.js:1:4353228)
    at ExternalApiService.handleServiceRequest (https://slobs-cdn.streamlabs.com/bundles/renderer.js:1:4416066)
    at ExternalApiService.handleServiceRequest (https://slobs-cdn.streamlabs.com/bundles/renderer.js:1:4353880)
    at ExternalApiService.executeServiceRequest (https://slobs-cdn.streamlabs.com/bundles/renderer.js:1:4414746)
    at https://slobs-cdn.streamlabs.com/bundles/renderer.js:1:4427036\n    at Array.forEach (<anonymous>)
    at TcpServerService.onRequestHandler (https://slobs-cdn.streamlabs.com/bundles/renderer.js:1:4426581)
    at SockJSConnection.<anonymous> (https://slobs-cdn.streamlabs.com/bundles/renderer.js:1:4425659)
    at SockJSConnection.emit (events.js:315:20)
    at RawWebsocketSessionReceiver.didMessage (https://slobs-cdn.streamlabs.com/bundles/vendors~renderer.js:2:3012954)
    at WebSocket.<anonymous> (https://slobs-cdn.streamlabs.com/bundles/vendors~renderer.js:2:3012714)
    at WebSocket.emit (events.js:315:20)
    at WebSocket.dispatchEvent (https://slobs-cdn.streamlabs.com/bundles/vendors~renderer.js:2:1561544)
    at WebSocket._receiveMessage (https://slobs-cdn.streamlabs.com/bundles/vendors~renderer.js:2:1559629)
    at Hybi.<anonymous> (https://slobs-cdn.streamlabs.com/bundles/vendors~renderer.js:2:1557494)
    at Hybi.emit (events.js:327:22)
    at Hybi.<anonymous> (https://slobs-cdn.streamlabs.com/bundles/vendors~renderer.js:2:4826078)
    at pipe (https://slobs-cdn.streamlabs.com/bundles/vendors~renderer.js:2:4843119)
    at Pipeline._loop (https://slobs-cdn.streamlabs.com/bundles/vendors~renderer.js:2:4843256)
    at Pipeline.processIncomingMessage (https://slobs-cdn.streamlabs.com/bundles/vendors~renderer.js:2:4842415)
    at Extensions.processIncomingMessage (https://slobs-cdn.streamlabs.com/bundles/vendors~renderer.js:2:4848355)
    at Hybi._emitMessage (https://slobs-cdn.streamlabs.com/bundles/vendors~renderer.js:2:4825769)
    at Hybi._emitFrame (https://slobs-cdn.streamlabs.com/bundles/vendors~renderer.js:2:4824871)
    at Hybi.parse (https://slobs-cdn.streamlabs.com/bundles/vendors~renderer.js:2:4819035)
    at IO.write (https://slobs-cdn.streamlabs.com/bundles/vendors~renderer.js:2:4836575)
    at Socket.ondata (_stream_readable.js:716:22)
    at Socket.emit (events.js:315:20)
    at addChunk (_stream_readable.js:295:12)
    at readableAddChunk (_stream_readable.js:271:9)
    at Socket.Readable.push (_stream_readable.js:212:10)
    at TCP.onStreamRead (internal/stream_base_commons.js:186:23)"}}

Expected behavior

It is expected that the server throws an INVALID_PARAMS = -32602 error with a message like "Scene not found".

Actual behavior

Internal server error is thrown instaed.