Fix #9804: Only apply sprite_zoom_min setting when sprites available (#9988)

Only discard sprite zoom levels when a suitable higher zoom level is
defined in the same colour mode

This is to avoid placeholder or empty sprites being used, causing
visual artefacts

src/spriteloader/spriteloader.hpp

@@ -72,9 +72,10 @@ public:
 	 * @param file_pos    The position within the file the image begins.
 	 * @param sprite_type The type of sprite we're trying to load.
 	 * @param load_32bpp  True if 32bpp sprites should be loaded, false for a 8bpp sprite.
+	 * @param control_flags Control flags, see SpriteCacheCtrlFlags.
 	 * @return Bit mask of the zoom levels successfully loaded or 0 if no sprite could be loaded.
 	 */
-	virtual uint8 LoadSprite(SpriteLoader::Sprite *sprite, SpriteFile &file, size_t file_pos, SpriteType sprite_type, bool load_32bpp) = 0;
+	virtual uint8 LoadSprite(SpriteLoader::Sprite *sprite, SpriteFile &file, size_t file_pos, SpriteType sprite_type, bool load_32bpp, byte control_flags) = 0;
 
 	virtual ~SpriteLoader() { }
 };