nrf_rpc: remove NULL pointer referenece

In case of error, the group pointer may be set to NULL.
This reverts part of changes introduced in the following PR:
nrfconnect#1493

Ref: NCSDK-29976

Signed-off-by: Tomasz Chyrowicz <[email protected]>

Author: tomchy

nrf_rpc/nrf_rpc.c

@@ -801,13 +801,7 @@ static void receive_handler(const struct nrf_rpc_tr *transport, const uint8_t *p
 	}
 
 	if (err < 0) {
-		internal_data.type = NRF_RPC_ERROR;
-		internal_data.group = group;
-		internal_data.err = err;
-		internal_data.hdr_id = hdr.id;
-		internal_data.hdr_type = hdr.type;
-		nrf_rpc_os_thread_pool_send((const uint8_t *)&internal_data, sizeof(internal_data));
-		nrf_rpc_os_event_wait(&group->data->decode_done_event, NRF_RPC_OS_WAIT_FOREVER);
+		nrf_rpc_err(err, NRF_RPC_ERR_SRC_RECV, group, hdr.id, hdr.type);
 	}
 }