connection: Handle empty signature and signature with just a version.
connection: Handle empty signature and signature with just a version.

Functions like wl_argument_from_va_list expect from get_next_argument,
to initialize details->type but when the signature is empty or contains
only version (like in desktop-shell-protocol.c in weston) it is left
uninitialized.

This patch fixes it, by initializing details->type with '\0' value,
signaling end of arguments.

Signed-off-by: Mariusz Ceier <78dc52caf5079969c88144cdfd5bacc084910d92@gmail.com>

tulcod/wayland,eyolfson/wayland,bitfactor/wayland,mchalupa/wayland,sir-murray/wayland,bitfactor/wayland,eyolfson/wayland,tulcod/wayland,mchalupa/wayland,abooij/wayland,abooij/wayland,sir-murray/wayland,mchalupa/wayland,tulcod/wayland,bitfactor/wayland,eyolfson/wayland,sir-murray/wayland,abooij/wayland