fix(shorebird_cli): gracefully handle failure to generate an aab diff

[bryanoltman]

Description

Print warning instead of crashing if we can't compute a diff between two aabs

Fixes #857

Type of Change

• ✨ New feature (non-breaking change which adds functionality)
• 🛠️ Bug fix (non-breaking change which fixes an issue)
• ❌ Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactor
• ✅ Build configuration change
• 📝 Documentation
• 🗑️ Chore

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (775fed6) 100.00% compared to head (25a1911) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #922   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           78        78           
  Lines         2833      2836    +3     
=========================================
+ Hits          2833      2836    +3     

Files Changed	Coverage Δ
...ebird_cli/lib/src/archive_analysis/aab_differ.dart	100.00% <100.00%> (ø)
.../lib/src/commands/patch/patch_android_command.dart	100.00% <100.00%> (ø)

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[felangel]

LGTM ✅