fixup! feat: use SCCNonlinearProblem for initialization

Author: AayushSabharwal

src/systems/diffeqs/abstractodesystem.jl

@@ -1315,8 +1315,8 @@ function InitializationProblem{iip, specialize}(sys::AbstractODESystem,
     end
 
     ts = get_tearing_state(isys)
-    if warn_initialize_determined &&
-       (unassigned_vars = StructuralTransformations.singular_check(ts); !isempty(unassigned_vars))
+    unassigned_vars = StructuralTransformations.singular_check(ts)
+    if warn_initialize_determined && !isempty(unassigned_vars)
         errmsg = """
         The initialization system is structurally singular. Guess values may \
         significantly affect the initial values of the ODE. The problematic variables \
@@ -1378,8 +1378,9 @@ function InitializationProblem{iip, specialize}(sys::AbstractODESystem,
                      end
         for (k, v) in u0map)
     end
-    TProb = if neqs == nunknown
-        use_scc ? SCCNonlinearProblem : NonlinearProblem
+
+    TProb = if neqs == nunknown && isempty(unassigned_vars)
+        use_scc && neqs > 0 && is_split(isys) ? SCCNonlinearProblem : NonlinearProblem
     else
         NonlinearLeastSquaresProblem
     end