Probably there is a short buffer in :

static void

dis_field_ud(tvbuff_t *tvb, proto_tree *tree, guint32 offset, guint32 length, gboolean udhi, guint8 udl,

    gboolean seven_bit, gboolean eight_bit, gboolean ucs2, gboolean compressed)

{

    static guint8  fill_bits_mask[NUM_FILL_BITS_MASKS] =

            { 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc };

    proto_item    *item;

    proto_item    *udh_item;

    proto_tree     *subtree = NULL;

    proto_tree     *udh_subtree = NULL;

    guint8           oct;

    guint fill_bits;

    guint32         out_len;

    char  *ustr;

    char        messagebuf[160];

Because when messsage is or more than 160 wireshark crashes.

Please may you review it.

Cecco