obexd/MAP: Fix crash when receiving an event report

obexd/MAP: Fix crash when receiving an event report

Conditional jump or move depends on uninitialised value(s)
   at 0x42C1AF: obex_put_stream_start (obex.c:869)
   by 0x428D1A: mns_put (mns.c:148)
   by 0x42B521: cmd_put (obex.c:982)
   by 0x419FB5: incoming_data (gobex.c:1022)
   by 0x3F31A47A54: g_main_context_dispatch (in /usr/lib64/libglib-2.0.so.0.3400.2)
   by 0x3F31A47D87: ??? (in /usr/lib64/libglib-2.0.so.0.3400.2)
   by 0x3F31A48181: g_main_loop_run (in /usr/lib64/libglib-2.0.so.0.3400.2)
   by 0x40DEE2: main (main.c:319)
 Uninitialised value was created by a stack allocation
   at 0x42C160: obex_put_stream_start (obex.c:862)