The fts3_tokenizer() function returns NULL if the

SQLITE_DBCONFIG_ENABLE_FTS_TOKENIZER setting is disabled, which is is
by default.

FossilOrigin-Name: f5732f4caf7a37a6445c61ae0d0ac14cc9deb897376e73aa36a1ead025b92c69

ext/fts3/README.tokenizers

@@ -52,8 +52,10 @@
 
   SECURITY: If the fts3 extension is used in an environment where potentially
     malicious users may execute arbitrary SQL (i.e. gears), they should be
-    prevented from invoking the fts3_tokenizer() function, possibly using the
-    authorisation callback.
+    prevented from invoking the fts3_tokenizer() function.  The
+    fts3_tokenizer() function is disabled by default. It is only enabled
+    by SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER. Do not enable it in
+    security sensitive environments.
 
   See "Sample code" below for an example of calling the fts3_tokenizer()
   function from C code.

ext/fts3/fts3_tokenizer.c

@@ -106,7 +106,9 @@ static void fts3TokenizerFunc(
       return;
     }
   }
-  sqlite3_result_blob(context, (void *)&pPtr, sizeof(pPtr), SQLITE_TRANSIENT);
+  if( fts3TokenizerEnabled(context) ){
+    sqlite3_result_blob(context, (void *)&pPtr, sizeof(pPtr), SQLITE_TRANSIENT);
+  }
 }
 
 int sqlite3Fts3IsIdChar(char c){