Exercise name should not auto-clear when getting focus

[ironjan]

Describe the feature you'd like
Hello,
when using the app for the first time, I noticed some peculiarities in the exercise editor. This is applicable to both "free workout" and the program exercise editor.

• Clearing exercise name on focus
  1. Enter an exercise name
  2. Move to another field
  3. Tap exercise name again (e.g. you noticed a typo)
  4. The input field. The name gets cleared.

Describe alternatives you've considered
Originally part of #147.