[Backend] Use the original functionTree instead an empty one

Belonging to [master]:
  - #2193

Author: Willi Braun

Compiler/BackEnd/SymbolicJacobian.mo

@@ -2106,10 +2106,10 @@ algorithm
       BackendDAE.ExtraInfo ei;
       Integer size;
 
-    case(BackendDAE.DAE(shared=BackendDAE.SHARED(cache=cache, graph=graph, info=ei)), {}, _, _, _, _, _, _) equation
+    case(BackendDAE.DAE(shared=BackendDAE.SHARED(cache=cache, graph=graph, info=ei, functionTree=functions)), {}, _, _, _, _, _, _) equation
       jacobian = BackendDAE.DAE( {BackendDAEUtil.createEqSystem(BackendVariable.emptyVars(), BackendEquation.emptyEqns())},
                                  BackendDAEUtil.createEmptyShared(BackendDAE.JACOBIAN(), ei, cache, graph));
-    then (jacobian, DAE.AvlTreePathFunction.Tree.EMPTY());
+    then (jacobian, functions);
 
     case( BackendDAE.DAE( BackendDAE.EQSYSTEM(orderedVars=orderedVars, orderedEqs=orderedEqs, matching=BackendDAE.MATCHING(ass2=ass2))::{},
                          BackendDAE.SHARED(globalKnownVars=globalKnownVars, cache=cache,graph=graph, functionTree=functions, info=ei) ),