[NF] Skip empty array variables and equations

Belonging to [master]:
  - #2738
  - OpenModelica/OpenModelica-testsuite#1060

Author: rfranke

Compiler/NFFrontEnd/NFConnector.mo

@@ -236,7 +236,9 @@ protected
               conns := splitImpl(c, t, face, source, cty, conns);
             end for;
           else
-            conns := CONNECTOR(name, ty, face, cty, source) :: conns;
+            if not Type.isEmptyArray(ty) then
+              conns := CONNECTOR(name, ty, face, cty, source) :: conns;
+            end if;
           end if;
         then
           conns;

Compiler/NFFrontEnd/NFInst.mo

@@ -97,6 +97,7 @@ import FlatModel = NFFlatModel;
 import ElementSource;
 import SimplifyModel = NFSimplifyModel;
 import Record = NFRecord;
+import Variable = NFVariable;
 import OperatorOverloading = NFOperatorOverloading;
 import EvalConstants = NFEvalConstants;
 
@@ -167,6 +168,9 @@ algorithm
   // Scalarize array components in the flat model.
   if Flags.isSet(Flags.NF_SCALARIZE) then
     flat_model := Scalarize.scalarize(flat_model, name);
+  else
+    // Remove empty arrays from variables
+    flat_model.variables := List.filterOnFalse(flat_model.variables, Variable.isEmptyArray);
   end if;
 
   // Convert the flat model to a DAE.

Compiler/NFFrontEnd/NFVariable.mo

@@ -84,5 +84,10 @@ public
       variable.attributes.variability <= Variability.STRUCTURAL_PARAMETER;
   end isStructural;
 
+  function isEmptyArray
+    input Variable variable;
+    output Boolean isEmpty = Type.isEmptyArray(variable.ty);
+  end isEmptyArray;
+
   annotation(__OpenModelica_Interface="frontend");
 end NFVariable;