[libxml2] Fix memory leak in xmlRegEpxFromParse

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 0b793591acccda4c4e8fe420cc9fe5ae8674b4f3
Author: zhouzhongyuan <zhouzhongyuan96 gmail com>
Date:   Mon Aug 26 15:24:12 2019 +0800

    Fix memory leak in xmlRegEpxFromParse
    
    Merge request !39

 xmlregexp.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/xmlregexp.c b/xmlregexp.c
index 9e9c3752..1e8bf934 100644
--- a/xmlregexp.c
+++ b/xmlregexp.c
@@ -545,6 +545,8 @@ xmlRegEpxFromParse(xmlRegParserCtxtPtr ctxt) {
        if (transitions == NULL) {
            xmlFree(stateRemap);
            xmlFree(stringRemap);
+            for (i = 0;i < nbatoms;i++)
+               xmlFree(stringMap[i]);
            xmlFree(stringMap);
            xmlFree(ret);
            return(NULL);