[9.x] Fixes `ensureDependenciesExist` runtime error

[nunomaduro]

This pull request fixes a small regression introduced on https://github.com/laravel/framework/pull/43367, where installing the necessary composer dependencies for "db:show", "db:table", and "model:show" is not causing the command to terminate, consequentially displays a runtime exception:

With this pull request, when doctrine/dbal is not installed for the current execution, we simply exit the command even if the user decides to install doctrine/dbal. Just like it was before https://github.com/laravel/framework/pull/43367.