Building flet standalone application

Question

I am on ubuntu 20.04 and I am trying to build a flet application with the command:

flet build linux

But it keeps displaying the error message below as shown below... Please who knows what the problem may be?

[22:48:11] Created Flutter bootstrap project from gh:flet-dev/flet-build-template with ref 0.25.2 ✅                                             
           Customized app icons and splash images ✅                                                                                             
[22:48:50] Generated app icons ✅                                                                                                                
[23:07:40] Flet app package app/app.zip was not created.                                                                                         
[23:11:45] Doctor summary (to see all details, run flutter doctor -v):                                                                           
           [✓] Flutter (Channel stable, 3.24.5, on Ubuntu 20.04.6 LTS 5.15.0-130-generic, locale en_US.UTF-8)                                    
           [✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0)                                                      
           [✓] Chrome - develop for the web                                                                                                      
           [✓] Linux toolchain - develop for Linux desktop                                                                                       
           [✓] Android Studio (version 2024.2)                                                                                                   
           [✓] VS Code (version 1.96.4)                                                                                                          
           [✓] Connected device (2 available)                                                                                                    
           [✓] Network resources                                                                                                                 
                                                                                                                                                 
           • No issues found!