[libxml2] Stop parser on unsupported encodings

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 0db8dc9ddcc0b5fb435b869668fb2155d491e245
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Wed Jun 7 16:07:33 2017 +0200

    Stop parser on unsupported encodings
    
    Otherwise, the push parser can loop infinitely in recover mode.
    
    Found with libFuzzer.

 parserInternals.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/parserInternals.c b/parserInternals.c
index bfc778a..b867cbc 100644
--- a/parserInternals.c
+++ b/parserInternals.c
@@ -1101,8 +1101,10 @@ xmlSwitchEncoding(xmlParserCtxtPtr ctxt, xmlCharEncoding enc)
                break;
        }
     }
-    if (handler == NULL)
+    if (handler == NULL) {
+        xmlStopParser(ctxt);
        return(-1);
+    }
     ctxt->charset = XML_CHAR_ENCODING_UTF8;
     ret = xmlSwitchToEncodingInt(ctxt, handler, len);
     if ((ret < 0) || (ctxt->errNo == XML_I18N_CONV_FAILED)) {