[libxslt] Fix heap overread in xsltFormatNumberConversion

[Nick Wellnhofer <nwellnhof src gnome org>]

commit eb1030de31165b68487f288308f9d1810fed6880
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Fri Jun 10 14:23:58 2016 +0200

    Fix heap overread in xsltFormatNumberConversion
    
    An empty decimal-separator could cause a heap overread. This can be
    exploited to leak a couple of bytes after the buffer that holds the
    pattern string.
    
    Found with afl-fuzz and ASan.

 libxslt/numbers.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/libxslt/numbers.c b/libxslt/numbers.c
index d1549b4..e78c46b 100644
--- a/libxslt/numbers.c
+++ b/libxslt/numbers.c
@@ -1090,7 +1090,8 @@ xsltFormatNumberConversion(xsltDecimalFormatPtr self,
     }
 
     /* We have finished the integer part, now work on fraction */
-    if (xsltUTF8Charcmp(the_format, self->decimalPoint) == 0) {
+    if ( (*the_format != 0) &&
+         (xsltUTF8Charcmp(the_format, self->decimalPoint) == 0) ) {
         format_info.add_decimal = TRUE;
        the_format += xsltUTF8Size(the_format); /* Skip over the decimal */
     }