title: "Cannot run with sound null safety" Flutter an existing Project?
body: <p>I had an existing application which i want to modify, I am using following dependencies:</p>
  <pre><code>  path_provider: ^2.0.8
    http: ^0.13.4
    html: ^0.15.0
    custom_pop_up_menu: ^1.2.2
    share: ^2.0.4
    connectivity: ^3.0.6
    flutter_swiper: ^1.1.6
  </code></pre>
  <p>Following error, i have even created a new empty project and added the dart files to that project but it is not working now.</p>
  <pre><code>    Error: Cannot run with sound null safety, because the following dependencies
  don't support null safety:
  
   - package:flutter_swiper
   - package:plugin_platform_interface
   - package:flutter_page_indicator
   - package:transformer_page_view
  </code></pre>