gc: reserve first block; lexer: free vstr.
diff --git a/py/lexer.c b/py/lexer.c
index 9ab0641..88bc0a1 100644
--- a/py/lexer.c
+++ b/py/lexer.c
@@ -635,6 +635,7 @@
         if (lex->stream_close) {
             lex->stream_close(lex->stream_data);
         }
+        vstr_clear(&lex->vstr);
         m_free(lex);
     }
 }