Index: ext/fts5/fts5_vocab.c
==================================================================
--- ext/fts5/fts5_vocab.c
+++ ext/fts5/fts5_vocab.c
@@ -558,11 +558,10 @@
         }
         if( pTab->eType==FTS5_VOCAB_INSTANCE ) break;
 
         if( rc==SQLITE_OK ){
           zTerm = sqlite3Fts5IterTerm(pCsr->pIter, &nTerm);
-          assert_nc( nTerm>0 );
           if( nTerm!=pCsr->term.n 
           || (nTerm>0 && memcmp(zTerm, pCsr->term.p, nTerm)) 
           ){
             break;
           }
@@ -619,10 +618,11 @@
       zTerm = (const char *)sqlite3_value_text(pGe);
       nTerm = sqlite3_value_bytes(pGe);
     }
     if( pLe ){
       const char *zCopy = (const char *)sqlite3_value_text(pLe);
+      if( zCopy==0 ) zCopy = "";
       pCsr->nLeTerm = sqlite3_value_bytes(pLe);
       pCsr->zLeTerm = sqlite3_malloc(pCsr->nLeTerm+1);
       if( pCsr->zLeTerm==0 ){
         rc = SQLITE_NOMEM;
       }else{

Index: ext/fts5/test/fts5vocab.test
==================================================================
--- ext/fts5/test/fts5vocab.test
+++ ext/fts5/test/fts5vocab.test
@@ -520,8 +520,27 @@
     lappend res $x(rowid)
   }
   db eval COMMIT
   set res
 } {3 5 7}
+
+do_execsql_test 10.6.1 {
+  SELECT * FROM t2 WHERE term<NULL;
+}
+do_execsql_test 10.6.2 {
+  SELECT * FROM t2 WHERE term>NULL;
+}
+do_execsql_test 10.6.3 {
+  SELECT * FROM t2 WHERE term=NULL;
+}
+do_execsql_test 10.7.1 {
+  SELECT * FROM t2 WHERE term<?;
+}
+do_execsql_test 10.7.2 {
+  SELECT * FROM t2 WHERE term>?;
+}
+do_execsql_test 10.7.3 {
+  SELECT * FROM t2 WHERE term=?;
+}
 
 finish_test