Tinkering with gperf options

src/json_tokens.gperf

@@ -3,11 +3,13 @@
 %}
 %define hash-function-name hash_json_token
 %define lookup-function-name lookup_json_token
-%language=C++
-%global-table
-%struct-type
-%readonly-tables
 %compare-lengths
+%global-table
+%language=C++
+%null-strings
+%readonly-tables
+%struct-type
+%switch=1
 
 struct JsonToken {
   const char* name;