You might have notices this behavior when you cut a selection or use the rubber tool.
The behavior depends on whether your images has an alpha channel.
You can add an alpha channel by choosing Layer → Transparency → Add alpha channel

Rails Long Term Support

Rails LTS provides security patches for old versions of Ruby on Rails (2.3, 3.2, 4.2 and 5.2)

Gimp: Why removing pixels sometimes leaves transparency, sometimes the background color