active_keyboard may be NULL, in which case an invalid pointer could be
passed to wlr_input_method_keyboard_grab_v2_send_modifiers. This
procedure call is unnecessary since wlroots commit 372a52ec "input
method: send modifiers in set_keyboard", so the call can simply be
removed.
Fixes#6836.
Before this commit, there would be cases where focus changes from one
window to another, the new window activates text_input, then the old
window sends a deactivate request, making text_input unfocused
completely.
Alexander Gramiak
xdavidwu
Tadeo Kondrak
Andri Yngvason
Leo