Taken as it's from:

http://git.gnome.org/browse/libxslt/commit/?id=abb7c65980c7da450f0447dcc6a1821eef99d473

From abb7c65980c7da450f0447dcc6a1821eef99d473 Mon Sep 17 00:00:00 2001
From: Nick Wellnhofer <[email protected]>
Date: Wed, 15 Aug 2012 21:06:14 +0000
Subject: Fix system-property with unknown namespace

The empty string should be returned, see bug #631803.
---
diff --git a/libxslt/functions.c b/libxslt/functions.c
index de962f4..01852b8 100644
--- a/libxslt/functions.c
+++ b/libxslt/functions.c
@@ -799,7 +799,9 @@ xsltSystemPropertyFunction(xmlXPathParserContextPtr ctxt, int nargs){
 	    } else {
 		valuePush(ctxt, xmlXPathNewString((const xmlChar *)""));
 	    }
-	}
+	} else {
+	    valuePush(ctxt, xmlXPathNewString((const xmlChar *)""));
+        }
 	if (name != NULL)
 	    xmlFree(name);
 	if (prefix != NULL)
diff --git a/tests/docs/bug-176.xml b/tests/docs/bug-176.xml
new file mode 100644
index 0000000..69d62f2
--- a/dev/null
+++ b/tests/docs/bug-176.xml
@@ -0,0 +1 @@
+<doc/>
diff --git a/tests/general/bug-176.out b/tests/general/bug-176.out
new file mode 100644
index 0000000..e829790
--- a/dev/null
+++ b/tests/general/bug-176.out
@@ -0,0 +1,2 @@
+<?xml version="1.0"?>
+<result/>
diff --git a/tests/general/bug-176.xsl b/tests/general/bug-176.xsl
new file mode 100644
index 0000000..6996e1e
--- a/dev/null
+++ b/tests/general/bug-176.xsl
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+               xmlns:msxsl="urn:schemas-microsoft-com:xslt"
+               exclude-result-prefixes="msxsl"
+               version="1.0">
+    <xsl:template match="/">
+        <result>
+            <xsl:value-of select="system-property('msxsl:version')"/>
+        </result>
+    </xsl:template>
+</xsl:transform>
--
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