fixed error reported on the list caused by my last change

* xmlstring.c: fixed error reported on the list caused by
  my last change
diff --git a/xmlstring.c b/xmlstring.c
index 5f239df..3617339 100644
--- a/xmlstring.c
+++ b/xmlstring.c
@@ -773,7 +773,7 @@
      *    11110xxx 10xxxxxx 10xxxxxx 10xxxxxx           valid 4-byte
      */
     for (ix = 0; (c = utf[ix]);) {      /* string is 0-terminated */
-        if (c & 0x80) {			/* 1-byte code, starts with 10 */
+        if ((c & 0x80) == 0x00) {	/* 1-byte code, starts with 10 */
             ix++;
 	} else if ((c & 0xe0) == 0xc0) {/* 2-byte code, starts with 110 */
 	    if ((utf[ix+1] & 0xc0 ) != 0x80)