Fix #123594: ICON_NONE Should be No Op

Using ICON_NONE causes textures to be referenced even though nothing
is ultimately drawn. This adds an early exit for this value, and also
changes the type of it from ICON_TYPE_COLOR_TEXTURE (used to display
a full-color bitmap) to ICON_TYPE_MONO_TEXTURE (normal one-color type
now coming from SVG).

Pull Request: https://projects.blender.org/blender/blender/pulls/123609

source/blender/editors/include/UI_icons.hh

@@ -38,7 +38,7 @@
 #endif
 
 /* ICON_ prefix added */
-DEF_ICON_COLOR(NONE)
+DEF_ICON(NONE)
 DEF_ICON(QUESTION)
 DEF_ICON(ERROR)
 DEF_ICON(CANCEL)

source/blender/editors/interface/interface_icons.cc

@@ -1853,6 +1853,10 @@ static void icon_draw_size(float x,
                            const IconTextOverlay *text_overlay,
                            const bool inverted = false)
 {
+  if (icon_id == ICON_NONE) {
+    return;
+  }
+
   bTheme *btheme = UI_GetTheme();
   const float fdraw_size = float(draw_size);