Fix fixing for events

src/build_sequences.jl

@@ -126,6 +126,7 @@ fixed(some_value) = some_value
 fixed(jump_variable::AbstractJuMPScalar) = value(jump_variable)
 fixed(jump_variable::AbstractArray) = fixed.(jump_variable)
 fixed(dict_variable::AbstractDict) = typeof(dict_variable)(k => fixed(v) for (k, v) in pairs(dict_variable))
+fixed(tuple_variable::Tuple) = fixed.(tuple_variable)
 fixed(pair:: Pair) = fixed(pair[1]) => fixed(pair[2])