594514 memory leaks - duplicate initialization

* globals.c: xmlInitGlobals() might be called multiple times, leaking
  the xmlThrDefMutex value
diff --git a/globals.c b/globals.c
index 9b4a551..1f807d8 100644
--- a/globals.c
+++ b/globals.c
@@ -46,7 +46,8 @@
  */
 void xmlInitGlobals(void)
 {
-    xmlThrDefMutex = xmlNewMutex();
+    if (xmlThrDefMutex != NULL)
+        xmlThrDefMutex = xmlNewMutex();
 }
 
 /**