backport: headless: fix uninitialized variable

We are using Weston with headless backend in Chromium to run tests with native Wayland backend. However, when we started to upgrade to weston 8 (our bots compile Weston from source), they started to fail. Reason - no output was created. This backport fixes that issue. Please consider to merge it. Thanks!

no_outputs is declared on the stack and left uninitialized if no weston option changing its value is provided.

Signed-off-by: Guillaume Champagne champagne.guillaume.c@gmail.com
Closes: #395 (closed)