Fix warning X4000: use of potentially uninitialized variable

[Antoshidza]

In unity 6 on Vulkan graphics API there is a warning: Shader warning in 'StencilDebug': use of potentially uninitialized variable (draw_digit) at kernel StencilDebug at StencilDebug.compute(39) (on vulkan) which happens because hlsl compiler is crazy and doesn't understand next code structure

if(predicate)
    return x;
return y;

It wants instead

if(predicate)
    return x;
else 
    return y;