Empty glyphs (like the space glyph) don’t have outlines but they do have an advance width. In a Glyph panel you can change an empty glyph into a simple glyph by adding contours. You can also change an empty glyph into a composite glyph by adding Composite Glyph Members.

Make Empty

Select Make Empty from the Edit menu, or the Make Empty toolbar button from the Tools toolbar to delete the outlines from a glyph. This will also remove any color data if performed from the Font panel. If this action is performed from within a glyph panel, then only the outline for the active layer will be deleted.