input/ipaccess.c: Check return value of osmo_fd_register()

Change-Id: I81659e0533ceb5d43292d97a63300b500044add7
Fixes: Coverity CID 57630
diff --git a/src/input/ipaccess.c b/src/input/ipaccess.c
index 1cb541e..35465e3 100644
--- a/src/input/ipaccess.c
+++ b/src/input/ipaccess.c
@@ -196,7 +196,12 @@
 			newbfd->priv_nr = E1INP_SIGN_RSL + unit_data.trx_id;
 			osmo_fd_unregister(bfd);
 			bfd->fd = -1;
-			osmo_fd_register(newbfd);
+			ret = osmo_fd_register(newbfd);
+			if (ret < 0) {
+				LOGP(DLINP, LOGL_ERROR,
+				     "could not register FD\n");
+				goto err;
+			}
 			/* now we can release the dummy RSL line. */
 			e1inp_line_put(line);
 		}