fix: fix ObservedWrapper for steady state systems

Author: AayushSabharwal

src/systems/problem_utils.jl

@@ -631,7 +631,9 @@ end
 ObservedWrapper{TD}(f::F) where {TD, F} = ObservedWrapper{TD, F}(f)
 
 function (ow::ObservedWrapper{true})(prob)
-    ow.f(state_values(prob), parameter_values(prob), current_time(prob))
+    # Edge case for steady state problems
+    t = applicable(current_time, prob) ? current_time(prob) : Inf
+    ow.f(state_values(prob), parameter_values(prob), t)
 end
 
 function (ow::ObservedWrapper{false})(prob)