Handle no tags in NodeHasTag.

Change-Id: Ibe3b0522c804a576c9505421bd8ffcd948332274
Signed-off-by: Austin Schuh <austin.schuh@bluerivertech.com>
diff --git a/aos/configuration.cc b/aos/configuration.cc
index 736f772..cbc9b8e 100644
--- a/aos/configuration.cc
+++ b/aos/configuration.cc
@@ -1287,6 +1287,10 @@
     return true;
   }
 
+  if (!node->has_tags()) {
+    return false;
+  }
+
   const auto *const tags = node->tags();
   return std::find_if(tags->begin(), tags->end(),
                       [tag](const flatbuffers::String *candidate) {