csn1: packet-csn1.c:179: warning: 'pui8' may be used uninitialized in this function

Port from wireshark.git commit fd9f182f4b13a3d81b1b5c797a6e4b9d6d327fdd.

Ported-by: Pau Espin Pedrol <pespin@sysmocom.de>
Change-Id: I37f5f3732f92cd7340af8ac1e04383f3e45e7636
diff --git a/src/csn1.cpp b/src/csn1.cpp
index 9ddb9c1..1174347 100644
--- a/src/csn1.cpp
+++ b/src/csn1.cpp
@@ -147,7 +147,7 @@
 {
   gint  remaining_bits_len = ar->remaining_bits_len;
   gint  bit_offset         = ar->bit_offset;
-  guint8*  pui8;
+  guint8*  pui8 = NULL;
   guint16* pui16;
   guint32* pui32;
   guint64* pui64;