[libxslt] Fix possible NULL pointer deref in xsltCopyTextString

[Nick Wellnhofer <nwellnhof src gnome org>]

commit f4611ecb4d212292c61feb8f1ba124f77a1c1e7c
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Sun Dec 13 19:32:29 2015 +0100

    Fix possible NULL pointer deref in xsltCopyTextString
    
    Based on the patch by mahendra.n. First part of fix for bug #757665.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=757665

 libxslt/transform.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/libxslt/transform.c b/libxslt/transform.c
index 24f9eb2..1c98254 100644
--- a/libxslt/transform.c
+++ b/libxslt/transform.c
@@ -929,9 +929,9 @@ xsltCopyTextString(xsltTransformContextPtr ctxt, xmlNodePtr target,
        }
        copy = xmlNewTextLen(string, len);
     }
+    if (copy != NULL && target != NULL)
+       copy = xsltAddChild(target, copy);
     if (copy != NULL) {
-       if (target != NULL)
-           copy = xsltAddChild(target, copy);
        ctxt->lasttext = copy->content;
        ctxt->lasttsize = len;
        ctxt->lasttuse = len;