Plug a mem leak

Plug a mem leak

Don't leak the ptr arrays in the map_sender_unique_name_to_signal_data_array
hash table.

==23440== 84 (20 direct, 64 indirect) bytes in 1 blocks are definitely lost in loss record 920 of 993
==23440==    at 0x4005BDC: malloc (vg_replace_malloc.c:195)
==23440==    by 0x4057094: g_malloc (gmem.c:134)
==23440==    by 0x406F2D6: g_slice_alloc (gslice.c:836)
==23440==    by 0x401D2D0: g_ptr_array_sized_new (garray.c:799)
==23440==    by 0x401D2AC: g_ptr_array_new (garray.c:783)
==23440==    by 0x420834A: g_dbus_connection_signal_subscribe (gdbusconnection.c:3084)

Bug #628436.