title: Dart Unhandled Exception: NoSuchMethodError: The method 'cast' was called on null. clevertap
body: <p>I am fetching a native display using  CleverTapPlugin.getDisplayUnitForId()</p>
  <p>var val = await CleverTapPlugin.getDisplayUnitForId(id);</p>
  <pre><code>[VERBOSE-2:shell.cc(93)] Dart Unhandled Exception: NoSuchMethodError: The method 'cast' was called on null.
  Receiver: null
  Tried calling: cast&lt;String, dynamic&gt;(), stack trace: #0      Object.noSuchMethod (dart:core-patch/object_patch.dart:63:5)
  
  
  Flutter 2.5.2 • channel stable • https://github.com/flutter/flutter.git
  Framework • revision 3595343e20 (3 months ago) • 2021-09-30 12:58:18 -0700
  Engine • revision 6ac856380f
  Tools • Dart 2.14.3
  #1      CleverTapPlugin.getDisplayUnitForId (package:clevertap_plugin/clevertap_plugin.dart:701:21)**strong text**
  </code></pre>