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/Sean_Barrett.json

@@ -4,12 +4,12 @@
     "author_handle" : "Sean_Barrett",
     "full_name" : "Sean Barrett",
     "sort_word" : "barrett",
-    "location_code" : "",
-    "location_name" : "",
+    "location_code" : null,
+    "location_name" : null,
     "email" : "buzzard@world.std.com",
     "url" : "http:\/\/world.std.com\/~buzzard",
     "alt_url" : null,
-    "deprecated_twitter_handle" : "",
+    "deprecated_twitter_handle" : null,
     "mastodon" : null,
     "mastodon_url" : null,
     "github" : null,