Merge pull request #15946 from MarianoGnu/issue_15870

Attemp to fix #15870

scene/resources/style_box.cpp

@@ -651,8 +651,8 @@ void StyleBoxFlat::draw(RID p_canvas_item, const Rect2 &p_rect) const {
 	}
 
 	//adapt borders (prevent weired overlapping/glitchy drawings)
-	int width = style_rect.size.width;
-	int height = style_rect.size.height;
+	int width = MAX(style_rect.size.width, 0);
+	int height = MAX(style_rect.size.height, 0);
 	int adapted_border[4] = { INT_MAX, INT_MAX, INT_MAX, INT_MAX };
 	adapt_values(MARGIN_TOP, MARGIN_BOTTOM, adapted_border, border_width, height, height, height);
 	adapt_values(MARGIN_LEFT, MARGIN_RIGHT, adapted_border, border_width, width, width, width);