correct author/author_handle.json empty strings

Fixed author/author_handle.json situations where "location_code",
"location_name", and/or "deprecated_twitter_handle" was an empty
JSON string.  In those cases the JSON null is used instead.

author/Peter_Klausler.json

@@ -9,7 +9,7 @@
     "email" : "pmk@cray.com",
     "url" : null,
     "alt_url" : null,
-    "deprecated_twitter_handle" : "",
+    "deprecated_twitter_handle" : null,
     "mastodon" : null,
     "mastodon_url" : null,
     "github" : null,