title: "ext.flutter.driver" is not found in "extensionRPCs" - What would be the issue?
body: <p>When I start running the appium flutter script, I get this error and wait for 5 minutes. After that it continues the execution.</p>
  
  <pre><code>[FlutterDriver] Attempt #1
  [FlutterDriver] Connecting to Dart Observatory: ws://127.0.0.1:39420/uVLSKORHloI=/ws
  [FlutterDriver] Connected to ws://127.0.0.1:39420/uVLSKORHloI=/ws
  [FlutterDriver] "ext.flutter.driver" is not found in "extensionRPCs" ["ext.ui.window.scheduleFrame"]
  [FlutterDriver] Cannot get Dart Isolate
  [FlutterDriver] Error: "ext.flutter.driver" is not found in "extensionRPCs" ["ext.ui.window.scheduleFrame"]
  [FlutterDriver]     at Object.wrappedLogger.errorAndThrow (/usr/local/lib/node_modules/appium-flutter-driver/node_modules/appium-support/lib/logging.js:74:35)
  [FlutterDriver]     at Client.onOpenListener (/usr/local/lib/node_modules/appium-flutter-driver/lib/sessions/observatory.ts:91:17)
  [FlutterDriver]     at runMicrotasks (&lt;anonymous&gt;)
  [FlutterDriver]     at processTicksAndRejections (internal/process/task_queues.js:93:5)
  [FlutterDriver] Waiting 300 seconds before trying...
  (node:71547) UnhandledPromiseRejectionWarning: Error: "ext.flutter.driver" is not found in "extensionRPCs" ["ext.ui.window.scheduleFrame"]
      at Object.wrappedLogger.errorAndThrow (/usr/local/lib/node_modules/appium-flutter-driver/node_modules/appium-support/lib/logging.js:74:35)
      at Client.onOpenListener (/usr/local/lib/node_modules/appium-flutter-driver/lib/sessions/observatory.ts:91:17)
      at runMicrotasks (&lt;anonymous&gt;)
      at processTicksAndRejections (internal/process/task_queues.js:93:5)
  (node:71547) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 3)
  </code></pre>
  
  <p>Whaat would be the issue?</p>