The bug

When loading a game profile which has been created and used in versions before 1.14 (or rather some of its pre-releases), for example 1.13.2, in 1.14 the following warning is logged:

Skipping bad option: textBackgroundOpacity:

or

Invalid floating point value for option textBackgroundOpacity = 
java.lang.NumberFormatException: empty String

In 22w14a, it logs the following error instead:

Error parsing option value  for option Text Background Opacity: Not a boolean: ""

How to reproduce

1. Create a new launcher profile with 1.13.2 as version
2. Start the version
3. In Minecraft click "Options" and "Done" to make sure the options.txt file is created
4. Change the profile version to 1.14 (or newer) and start it
   → The warning is logged