check return value from close() after write()

otherwise we may lose data when quota is exceeded
or nfs is in a bad mood.

src/drv_maildir.c

@@ -1028,7 +1028,11 @@ maildir_store_msg( store_t *gctx, msg_data_t *data, int to_trash,
 		close( fd );
 		return cb( DRV_BOX_BAD, 0, aux );
 	}
-	close( fd );
+	if (close( fd ) < 0) {
+		/* Quota exceeded may cause this. */
+		perror( buf );
+		return cb( DRV_BOX_BAD, 0, aux );
+	}
 	/* Moving seen messages to cur/ is strictly speaking incorrect, but makes mutt happy. */
 	nfsnprintf( nbuf, sizeof(nbuf), "%s%s/%s/%s%s", prefix, box, subdirs[!(data->flags & F_SEEN)], base, fbuf );
 	if (rename( buf, nbuf )) {