Don't die on noteOff events that have had no corresponding noteOn
Don't die on noteOff events that have had no corresponding noteOn

bradparks/jasmid,darrylyeo/jasmid,garzon/jasmid,jsphweid/midiAnalysis,bradparks/jasmid,garzon/jasmid,garzon/jasmid,darrylyeo/jasmid,bradparks/jasmid,jsphweid/midiAnalysis,jsphweid/midiAnalysis,darrylyeo/jasmid