ensure default-constructed Selectors is empty

refs #3944

Change-Id: Iaf5b6176529c4533214c4e27069734f8bdb7e556
diff --git a/src/selectors.cpp b/src/selectors.cpp
index dc741a3..8890b58 100644
--- a/src/selectors.cpp
+++ b/src/selectors.cpp
@@ -52,7 +52,7 @@
          m_maxSuffixComponents < 0 &&
          m_publisherPublicKeyLocator.empty() &&
          m_exclude.empty() &&
-         m_childSelector < 0 &&
+         m_childSelector == DEFAULT_CHILD_SELECTOR &&
          !m_mustBeFresh;
 }