rawmidi: skip check of return value from g_malloc()

rawmidi: skip check of return value from g_malloc()

In GLib implementation, the call of g_malloc() can bring program abort
due to memory starvation. This is necessarily preferable because applications
cannot handle the case and GLib has alternative APIs named 'try' to
allow applications to handle the case.

On the other hand, the memory starvation is system wide issue and it's
hard for applications to solve the issue. It's reasonable for the
implementation to have program abort somehow.

Furthermore, the call of g_object_new() can bring program abort due
to memory starvation. It's impossible for applications to handle the
case.

This commit skips check of return value from g_malloc().

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>