Fixed EvalEvaluator when there is nothing to evaluate

tests/test_sheerka_non_reg.py

@@ -400,3 +400,19 @@ def test_i_can_say_that_a_concept_isa_another_concept():
     res = sheerka.evaluate_user_input("foo isa bar")
     assert res[0].status
     assert sheerka.isinstance(res[0].body, BuiltinConcepts.SUCCESS)
+
+
+def test_eval_does_not_break_valid_result():
+    sheerka = get_sheerka()
+    sheerka.evaluate_user_input("def concept one as 1")
+    sheerka.evaluate_user_input("def concept two as 2")
+
+    res = sheerka.evaluate_user_input("one + two")
+    assert len(res) == 1
+    assert res[0].status
+    assert res[0].body == 3
+
+    res = sheerka.evaluate_user_input("eval one + two")
+    assert len(res) == 1
+    assert res[0].status
+    assert res[0].body == 3