support SDPs with empty unicast address in origin (#121)

go.mod

@@ -5,7 +5,7 @@ go 1.15
 require (
 	github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751 // indirect
 	github.com/alecthomas/units v0.0.0-20190924025748-f65c72e2690d // indirect
-	github.com/aler9/gortsplib v0.0.0-20201111093850-5962a481ef10
+	github.com/aler9/gortsplib v0.0.0-20201112104820-ad96344f01fe
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/fsnotify/fsnotify v1.4.9
 	github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51

go.sum

@@ -2,8 +2,8 @@ github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751 h1:JYp7IbQjafo
 github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751/go.mod h1:LOuyumcjzFXgccqObfd/Ljyb9UuFJ6TxHnclSeseNhc=
 github.com/alecthomas/units v0.0.0-20190924025748-f65c72e2690d h1:UQZhZ2O0vMHr2cI+DC1Mbh0TJxzA3RcLoMsFw+aXw7E=
 github.com/alecthomas/units v0.0.0-20190924025748-f65c72e2690d/go.mod h1:rBZYJk541a8SKzHPHnH3zbiI+7dagKZ0cgpgrD7Fyho=
-github.com/aler9/gortsplib v0.0.0-20201111093850-5962a481ef10 h1:vJ0eBvkr8mfQ2TS/w+Ta8dbSRnLv/Ct0lBcPdMnwZIM=
-github.com/aler9/gortsplib v0.0.0-20201111093850-5962a481ef10/go.mod h1:6yKsTNIrCapRz90WHQtyFV/rKK0TT+QapxUXNqSJi9M=
+github.com/aler9/gortsplib v0.0.0-20201112104820-ad96344f01fe h1:se/lGBXWvJzIhUCKfvH/FDJQ4aFzbC/782fnIOcXK8A=
+github.com/aler9/gortsplib v0.0.0-20201112104820-ad96344f01fe/go.mod h1:6yKsTNIrCapRz90WHQtyFV/rKK0TT+QapxUXNqSJi9M=
 github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=