Fix constants handling in ODAEProblem

Author: YingboMa

src/structural_transformation/codegen.jl

@@ -187,8 +187,13 @@ function gen_nlsolve!(is_not_prepended_assignment, eqs, vars, u0map::AbstractDic
 
     fname = gensym("fun")
     # f is the function to find roots on
-    funex = isscalar ? rhss[1] : MakeArray(rhss, SVector)
-    pre = get_preprocess_constants(funex)
+    if isscalar
+        funex = rhss[1]
+        pre = get_preprocess_constants(funex)
+    else
+        funex = MakeArray(rhss, SVector)
+        pre = get_preprocess_constants(rhss)
+    end
     f = Func([DestructuredArgs(vars, inbounds = !checkbounds)
               DestructuredArgs(params, inbounds = !checkbounds)],
              [],