rrc: fix RLF re-establishment crash -- address peer teardown with leg-correct node id

handleRadioLinkFailure drives the symmetric teardown on the peer via
peerBm->releaseLink(myId), where myId identifies the failing node to the peer: the
peer deletes its PDCP/RLC/MAC entities for this link keyed by that id (the source/dest
id it saw on the bearer). myId was hardcoded to registration_->getLteNodeId(), which is
NODEID_NONE on a standalone NR gNB (a GNODEB stores its id in nrNodeId; see
Registration). So the peer UE received 0, its keyed PDCP deletion (kept per-node to
protect the other leg in DC) matched nothing, and pdcp-rx-<gnb>-<drb> survived -- while
the UE-side RLC deletion (wipe-all) removed the RLC entity. On the first post-reconnect
DL packet the on-demand rebuild then hit 'Cannot insert module pdcp-rx-1-1 ... already
exists' and aborted.

Address the peer with our id on the FAILING leg instead:
  myId = nrStack ? registration_->getNrNodeId() : registration_->getLteNodeId();
This is the id the peer actually keyed by, so its keyed PDCP deletion now removes the
stale entity and re-establishment rebuilds cleanly. Latent since the DRB teardown became
duplex (the cross-node symmetric releaseLink is the bidirectional half); the mismatched
field is the node id, not the drbId.

Validated (nr/standalone VoIP-DL-AM-Lossy, forced RLF via maxRtxThreshold=1 maxHarqRtx=0,
t311=1s t301=0.1s): run is now crash-free through the full 5s, teardown addresses the UE
with the gNB's NR id (1, was 0), and DL delivery RESUMES -- 113 UE deliveries, 95 of them
after the reconnect at t=1.529s (parent: crashed at 18, none after). Fingerprint suite
137/137 PASS byte-identical (default t311=0 => RLF path not exercised).

Author: avarga

src/simu5g/stack/rrc/BearerManagement.cc

@@ -134,7 +134,12 @@ void BearerManagement::handleRadioLinkFailure(MacNodeId nodeId, bool nrStack)
     // bearer rebuilds fresh, SN-consistent entities on both sides. Reaching the peer via the
     // binder mirrors handover's cross-node HandoverController::deleteOldBuffers.
     releaseLink(nodeId);
-    MacNodeId myId = registration_->getLteNodeId();
+    // Address the peer's symmetric teardown with OUR node id on the failing leg: the peer keys
+    // its entities (PDCP/RLC/MAC) for this link by that id (the source/dest id it saw on the
+    // bearer). Using getLteNodeId() unconditionally sent NODEID_NONE from a standalone NR gNB
+    // (whose id lives in nrNodeId), so the peer's keyed PDCP deletion missed pdcp-rx-<gnb>-<drb>
+    // and a later re-establishment collided with the leftover entity.
+    MacNodeId myId = nrStack ? registration_->getNrNodeId() : registration_->getLteNodeId();
     if (cModule *peerRrc = binderModule->getRrcByNodeId(nodeId)) {
         if (auto *peerBm = dynamic_cast<BearerManagement *>(peerRrc->getSubmodule("bearerManagement")))
             peerBm->releaseLink(myId);