common/helpers: avoid use of uninitialized variable
common/helpers: avoid use of uninitialized variable

../../tests/common/helpers.cpp: In function ‘int GetNMonitors(Display*)’:
../../tests/common/helpers.cpp:96:12: warning: ‘n_active_outputs’ may be
used uninitialized in this function [-Wmaybe-uninitialized]
../../tests/common/helpers.cpp: In function ‘void
GetMonitorGeometry(Display*, int, int*, int*, int*, int*)’:
../../tests/common/helpers.cpp:128:27: warning: ‘n_active_outputs’ may be
used uninitialized in this function [-Wmaybe-uninitialized]

Signed-off-by: Peter Hutterer <b9c50af7afa7642f6f854434cda9ffe54ece8b85@who-t.net>

freedesktop-unofficial-mirror/xorg__test__xorg-integration-tests,freedesktop-unofficial-mirror/xorg__test__xorg-integration-tests,freedesktop-unofficial-mirror/xorg__test__xorg-integration-tests