xwayland: Initialise values in xwlVidModeGetGamma()
ProcVidModeGetGamma() relies on GetGamma() to initialise values if it returns TRUE. Without this, we're sending uninitialised values to clients. Fixes: xorg/xserver#1040
ProcVidModeGetGamma() relies on GetGamma() to initialise values if it returns TRUE. Without this, we're sending uninitialised values to clients. Fixes: xorg/xserver#1040