TestQueryer: actually check Rows returned

Fixes a test which did not correctly exercise the multi-statement
Queryer functionality

sqlite3_test.go

@@ -1080,7 +1080,6 @@ func TestQueryer(t *testing.T) {
 	}
 	defer rows.Close()
 	n := 1
-	if rows != nil {
 	for rows.Next() {
 		var id int
 		err = rows.Scan(&id)
@@ -1090,7 +1089,10 @@ func TestQueryer(t *testing.T) {
 		if id != n {
 			t.Error("Failed to db.Query: not matched results")
 		}
+		n = n + 1
 	}
+	if n != 3 {
+		t.Errorf("Expected 3 rows but retrieved %v", n-1)
 	}
 }