Fixed race condition when innobase_shutdown_for_mysql() was called before...

Fixed race condition when innobase_shutdown_for_mysql() was called before parser was initialized (as it's initialized on first usage)

storage/xtradb/pars/lexyy.c

@@ -2786,7 +2786,9 @@ void
 pars_lexer_close(void)
 /*==================*/
 {
+        if (yy_buffer_stack)
           yylex_destroy();
+        if (stringbuf)
 	  free(stringbuf);
 	stringbuf = NULL;
 	stringbuf_len_alloc = stringbuf_len = 0;

storage/xtradb/pars/pars0lex.l

@@ -669,7 +669,9 @@ void
 pars_lexer_close(void)
 /*==================*/
 {
+        if (yy_buffer_stack)
   	  yylex_destroy();
+        if (stringbuf)
   	  free(stringbuf);
 	stringbuf = NULL;
 	stringbuf_len_alloc = stringbuf_len = 0;