Fixed EvalEvaluator when there is nothing to evaluate

tests/test_sheerka_call_evaluators.py

@@ -162,6 +162,28 @@ class EvaluatorAllReduceFooBar(EvaluatorAllWithPriority):
         return ret
 
 
+class EvaluatorAllSuppressFooEntry(EvaluatorAllWithPriority):
+
+    def __init__(self):
+        super().__init__("suppress", 100)
+
+    def matches(self, context, return_values):
+        super().matches(context, return_values)
+        return True
+
+    def eval(self, context, return_values):
+        super().eval(context, return_values)
+        foo = None
+        for ret in return_values:
+            if ret.body.name == "foo":
+                foo = ret
+
+        if foo:
+            return context.sheerka.ret(self.name, False, Concept("does not matter"), parents=[foo])
+        else:
+            return None
+
+
 def test_that_return_values_is_unchanged_when_no_evaluator():
     sheerka = get_sheerka()
     sheerka.evaluators = []