Improve treatment of nregativity in SpanWithinQueries

Change-Id: I84ca40cdaef150211963da857cd6eab9c9e44db7
diff --git a/Changes b/Changes
index 47f9b2f..06d3996 100644
--- a/Changes
+++ b/Changes
@@ -10,6 +10,7 @@
           a single extension, if possible (diewald)
         - [bugfix] Fixed paths in test suite for supporting
           spaces (margaretha)
+        - [bugfix] Warn on empty elements in positional queries (diewald)
 
 0.55.6 2016-08-10
         - [bugfix] distance with key "t" uses default foundry (diewald)