Segmentation fault on resize empty window.

[vbalyasnyy]

Segmentation fault on next simple code:

int main(void)
{
    LCUI_Init();
    LCUIDisplay_SetSize(320, 239);
    return LCUI_Main();
}

Steps to reproduce the behavior:

1. Compile example above.
2. Launch it.

Environment:

• LCUI version: 1.3.0
• Build tools: gcc 8.3.0
• OS and version: Ubuntu 18.10

Reason of crash:

• in commit https://github.com/lc-soft/LCUI/commit/13c84b2a6a317a79113c6314aca17f2130921b63 used default prototype by default, that have non-empty paint handler pointer (NULL used by default for proto before this fix).

• with default protoype for all widgets function src/gui/widget_paint.c:Widget_IsPaintable() returns true.

• that is why in render function return non-zero count for empty window, cause src/gui/widget_paint.c:WidgetRenderer() function setup that->can_render_self = Widget_IsPaintable(w) always true.

p.s. but, if use LCUIDisplay_SetSize(321, 241) in example, it is not crashed, couse it updates correctly and creates surface->pixmap and surface->gc and empty widget render successfully