[DRE-maint] Bug#1068332: schleuder: throws a traceback if told to import a key, but a key can't be found

[Georg Faerber]

Package: schleuder
Version: 4.0.3-7
Forwarded: https://0xacab.org/schleuder/schleuder/-/issues/526
Tags: bookworm fixed-upstream upstream

Super admins receive the following error via mail if a user tries to
import a key via a request mail with x-add-key, but no key:

undefined method `compact' for "Your message did not contain any attachments nor text content. Therefore no key could be imported.":String

        import_stati = results.compact.collect(&:imports).flatten
                              ^^^^^^^^
/usr/lib/ruby/vendor_ruby/schleuder/keyword_handlers/key_management.rb:21:in `add_key'
/usr/lib/ruby/vendor_ruby/schleuder/keyword_handlers_runner.rb:67:in `run_handler'
/usr/lib/ruby/vendor_ruby/schleuder/keyword_handlers_runner.rb:34:in `block in run'
/usr/lib/ruby/vendor_ruby/schleuder/keyword_handlers_runner.rb:32:in `map'
/usr/lib/ruby/vendor_ruby/schleuder/keyword_handlers_runner.rb:32:in `run'
/usr/lib/ruby/vendor_ruby/schleuder/filters/post_decryption/10_request.rb:16:in `request'
/usr/lib/ruby/vendor_ruby/schleuder/filters_runner.rb:14:in `block in run'
/usr/lib/ruby/vendor_ruby/schleuder/filters_runner.rb:12:in `map'
/usr/lib/ruby/vendor_ruby/schleuder/filters_runner.rb:12:in `run'
/usr/lib/ruby/vendor_ruby/schleuder/runner.rb:127:in `run_filters'
/usr/lib/ruby/vendor_ruby/schleuder/runner.rb:56:in `run'
/usr/lib/ruby/vendor_ruby/schleuder/cli.rb:38:in `work'
/usr/share/rubygems-integration/all/gems/thor-1.2.1/lib/thor/command.rb:27:in `run'
/usr/share/rubygems-integration/all/gems/thor-1.2.1/lib/thor/invocation.rb:127:in `invoke_command'
/usr/share/rubygems-integration/all/gems/thor-1.2.1/lib/thor.rb:392:in `dispatch'
/usr/share/rubygems-integration/all/gems/thor-1.2.1/lib/thor/base.rb:485:in `start'
/usr/bin/schleuder:13:in `<main>'