Determine whether there's an Allen-wrench port at the bottom of the disposal, which is located under the sink. If there is, insert an Allen-wrench into the port and turn it back and forth to move the masher plate and dislodge the glass. If you can't find an Allen-wrench port, insert the handle of a broom or a hammer into the top of the garbage disposal and wiggle it around to try to dislodge the glass.
Another common cause for a leaking garbage disposal is the disposal flange. A leak at the very most upper area of the garbage disposal could be the garbage disposal flange which goes through the sink. A garbage disposal flange should be sealed with Plumber’s putty and then tightened from underneath the sink. If this is not tight enough or if it has managed to come loose (which can happen) then the garbage disposal will have to be taken down so the flange can be resealed and then the garbage disposal can be rehung.