[548388] Don't generate variables for a variable with an ID

https://bugs.eclipse.org/bugs/show_bug.cgi?id=548388
diff --git a/plugins/org.eclipse.oomph.setup.core/src/org/eclipse/oomph/setup/internal/core/SetupTaskPerformer.java b/plugins/org.eclipse.oomph.setup.core/src/org/eclipse/oomph/setup/internal/core/SetupTaskPerformer.java
index ecb027e..84929a8 100644
--- a/plugins/org.eclipse.oomph.setup.core/src/org/eclipse/oomph/setup/internal/core/SetupTaskPerformer.java
+++ b/plugins/org.eclipse.oomph.setup.core/src/org/eclipse/oomph/setup/internal/core/SetupTaskPerformer.java
@@ -646,7 +646,7 @@
           SetupTask setupTask = it.next();
 
           String id = setupTask.getID();
-          if (!StringUtil.isEmpty(id))
+          if (!StringUtil.isEmpty(id) && !(setupTask instanceof VariableTask))
           {
             EClass eClass = setupTask.eClass();
             for (EAttribute eAttribute : eClass.getEAllAttributes())