restricted to add empty number into field

Description

resolved Crash was observed when keepin the Number of days blank and tapping on SAVE

now user need to add some number before tapping on SAVE

Issue(s)

https://gitlab.e.foundation/e/os/backlog/-/issues/143

Test environment

1. Download apk https://gitlab.e.foundation/e/os/Message/-/jobs/281422/artifacts/browse/presentation/build/outputs/apk/noAnalytics/debug/
2. Transfer apk to your device.
3. Find the apk from the fileManager. Click & install it.
4. There should be a new mail icon in your device home-page (you will find 2 total mail apps, select the latest entry one).

Steps to reproduce

• Launch the Message app
• Tap on triple horizontal lines on the top left corner
• Tap on settings
• Scroll down to Delete old messages automatically
• Leave the number of days blank and tap on SAVE

Test procedures

Technical details

Screenshots

Check list

• Self review
• Test procedure explained
• Tested on fresh install
• Tested applied as an update
• License
• Internal documentation
• User documentation