Fixed visitors to expect 2 elements at least

interface/HUTN/hutn_compiler/constructors_visitor.py

@@ -260,7 +260,7 @@ class ConstructorsVisitor(Visitor):
 
     def visit_return(self, tree):
         self.add_constructors('"return"')
-        if len(tree.get_tail()) > 1:
+        if len(tree.get_tail()) > 2:
             self.add_constructors('true')
             self.visit(tree.get_tail()[1])
         else:

interface/HUTN/hutn_compiler/primitives_visitor.py

@@ -443,7 +443,7 @@ class PrimitivesVisitor(Visitor):
         self.visit_children(tree)
         r = self.value("return")
         self.debug(r, tree)
-        if len(tree.get_tail()) > 1:
+        if len(tree.get_tail()) > 2:
             v = self.get_primitive(tree.get_tail()[1])
             self.dict(r, "value", v)
         self.set_primitive(tree, r)