No Send button, or Attach button or Menu button in draft emails if using System Default or Light themes

Checklist

• I have used the search function to see if someone else has already submitted the same bug report.
• I will describe the problem with as much detail as possible.

App

K-9 Mail

App version

18.0

Where did you get the app from?

Google Play

Android version

8.0.0

Device model

Galaxy S7

Steps to reproduce

1. Create a draft email, while using the Light or System Default theme.

2. There is no Send, Attach or Menu button in the draft email, as shown in this screen capture.

[Note - if you normally use the Dark theme, this problem may take up to a few hours to become apparent.]

3. If you then switch to the Dark theme and back to the Light or System Default theme the problem temporarily disappears - i.e. if you then create a draft email, the Send, Attach and Menu buttons will now be visible, as shown in this screen capture.

4. However if you continue to use the Light or System Default theme, then after a while (sometimes a few minutes, sometimes a few hours), the Send, Attach & Menu buttons will again not be visible in draft emails.

Note: This problem never occurred prior to the release of K-9 Mail version 18.0.

Expected behavior

The Send, Attach & Menu buttons should always be visible in draft emails.

Actual behavior

See above.

Logs

No response

Reproduce the issue in K-9 Mail 18.0 on Android 8.0 using a draft email and the Light or System Default theme; compare the draft editor before and after switching themes. Trace the theme-related draft editor UI, and consider the issue done when Send, Attach, and Menu remain visible while continuing to use those themes.