[NF] Don't split external objects in connectors.

Belonging to [master]:
  - #3013
  - OpenModelica/OpenModelica-testsuite#1153

Author: perost

Compiler/NFFrontEnd/NFConnector.mo

@@ -254,6 +254,9 @@ protected
         then
           conns;
 
+      case Type.COMPLEX(complexTy = ComplexType.EXTERNAL_OBJECT())
+        then CONNECTOR(name, Type.liftArrayLeftList(ty, dims), face, cty, source) :: conns;
+
       case Type.COMPLEX()
         algorithm
           tree := Class.classTree(InstNode.getClass(ty.cls));