oss: fix dangling descriptor value (refs #10772)

modules/audio_output/oss.c

@@ -103,7 +103,6 @@ static int Start (audio_output_t *aout, audio_sample_format_t *restrict fmt)
                  vlc_strerror_c(errno));
         return VLC_EGENERIC;
     }
-    sys->fd = fd;
     msg_Dbg (aout, "using OSS device: %s", device);
 
     /* Select audio format */
@@ -215,6 +214,7 @@ static int Start (audio_output_t *aout, audio_sample_format_t *restrict fmt)
     }
     aout_FormatPrepare (fmt);
 
+    sys->fd = fd;
     VolumeSync (aout);
     sys->starting = true;
     sys->format = *fmt;