Fix memory management issues

Fix memory management issues

atspi/atspi-mutter.c

Dynamic memory referenced by 'name' was allocated at
atspi-accessible.c:307 by calling function 'atspi_accessible_get_name'
at atspi-mutter.c:398 and lost at atspi-mutter.c:401.

Pointer '&data.rd_session_path[0]' returned from function 'g_strdup' at
atspi-mutter.c:82 may be null, and it is dereferenced at
atspi-mutter.c:83.

atspi/atspi-event-listener.c

Return value of a function '_atspi_dbus_return_accessible_from_iter' is
dereferenced at atspi-event-listener.c:1094 without checking, but it is
usually checked for this function (5/6).

Change-Id: Ie311948f4d8f71025d0b1769a97e2904ee4af387