Two bugs with the spacebar in lablgtk3-sourceview3

[Frigory33]

Hello. I am a CoqIDE user and I am facing two problems with usage of the spacebar of my keyboard.

1. When pressing space after a backslash, the backslash is removed, no space is inserted, and you get a delta Δ instead. (In CoqIDE, this is annoying when typing /\.)
2. When something else than the editor has the focus and I press space, then… it inserts a space in the GtkSourceView editor. (In CoqIDE, this is annoying for the Search field: I have to copy-paste a space to be able to search for text containing space.)

The two bugs can be combined if you want.

I think this comes from version 3.1.5, since I don’t see it in all configs and it started last summer. I’m not completely sure it does not come from CoqIDE itself, but it seems improbable. Can you confirm these bugs come from you?