Fix TextureProgressBar radial mode invalid polygon edge case

[kleonc]

TextureProgressBar::unit_val_to_uv(float val) can produce exactly the same UV for almost equal values. Currently subsequent points on the TextureProgressBar's edge mapped to the same UV would be skipped, which can lead to trying to create a 2-point polygon created from from and center (in case to would be skipped because it is close enough to from so unit_val_to_uv(from) == unit_val_to_uv(to)).

godot/scene/gui/texture_progress_bar.cpp

Lines 527 to 531 in 1ce6df7

	for (const float &f : pts) {
	Point2 uv = unit_val_to_uv(f);
	if (uvs.has(uv)) {
	continue;
	}

This PR leaves skipping same-UV points as is, and just ensure points.size() >= 3 before rendering a polygon.

Alternative would be to try improve precision/robustness of TextureProgressBar::unit_val_to_uv(float val) but it's probably not needed as the issue happens in an edge case (a super thin triangle which would likely not be rendered anyway).

Fixes #92790.

[akien-mga]

Thanks!