Handle NULL file names. From Roland Ortloff.

lib/zip_close.c

diff --git a/lib/zip_close.c b/lib/zip_close.c
index 9bd53f6..fbd8bdf 100644
--- a/lib/zip_close.c
+++ b/lib/zip_close.c
@@ -630,6 +630,13 @@
 static int
 _zip_torrentzip_cmp(const void *a, const void *b)
 {
-    return strcasecmp(((const struct zip_filelist *)a)->name,
-		      ((const struct zip_filelist *)b)->name);
+    const char *aname = ((const struct zip_filelist *)a)->name;
+    const char *bname = ((const struct zip_filelist *)b)->name;
+
+    if (aname == NULL)
+	return (bname != NULL) * -1;
+    else if (bname == NULL)
+	return 1;
+
+    return strcasecmp(aname, bname);
 }