Make sure that px_opa is initialized in lv_draw_letter
Make sure that px_opa is initialized in lv_draw_letter

Make sure that the variable px_opa in lv_draw_letter is initialized,
else a compile time warring will occur .

Signed-off-by: Jan Van Winkel <d648848808a4d751aff880668aa63d2d9d94a5a4@dxplore.eu>

littlevgl/lvgl,littlevgl/lvgl,littlevgl/lvgl,littlevgl/lvgl