Apply suggestions from code review

Co-authored-by: J.C. Jones <james.jc.jones@gmail.com>

Author: weebl2000

src/helpers/BaseChatMesh.cpp

@@ -1325,7 +1325,10 @@ uint8_t BaseChatMesh::handleIncomingSessionKeyInit(ContactInfo& from, const uint
 
   // 4. Store in pool (dual-decode: new key active, old key still valid)
   auto entry = allocateSessionKey(from.id.pub_key);
-  if (!entry) return 0;
+  if (!entry) {
+    memset(new_session_key, 0, SESSION_KEY_SIZE);
+    return 0;
+  }
 
   if (entry->state == SESSION_STATE_ACTIVE || entry->state == SESSION_STATE_DUAL_DECODE) {
     memcpy(entry->prev_session_key, entry->session_key, SESSION_KEY_SIZE);

src/helpers/ClientACL.cpp

@@ -264,7 +264,10 @@ int ClientACL::handleSessionKeyInit(const ClientInfo* client, const uint8_t* eph
 
   // 4. Store in pool (dual-decode: new key active, old key still valid)
   auto entry = allocateSessionKey(client->id.pub_key);
-  if (!entry) return 0;
+  if (!entry) {
+    memset(new_session_key, 0, SESSION_KEY_SIZE);
+    return 0;
+  }
 
   if (entry->state == SESSION_STATE_ACTIVE || entry->state == SESSION_STATE_DUAL_DECODE) {
     memcpy(entry->prev_session_key, entry->session_key, SESSION_KEY_SIZE);