Null-check packet allocations in allocForSending and its callers (#11086)

* Null-check packet allocations in allocForSending and its callers

Sibling of 0ae44d701.

* Null-check allocDataProtobuf, allocAckNak and allocErrorResponse callers

Second tier of the same nullable contract.

* Keep telemetry sleep scheduling on allocation failure

Allocation failure now marks the telemetry invalid instead of returning
early, so power-saving SENSOR nodes still arm deep sleep.

src/mesh/MeshModule.cpp

@@ -57,6 +57,8 @@ meshtastic_MeshPacket *MeshModule::allocAckNak(meshtastic_Routing_Error err, Nod
     // So we manually call pb_encode_to_bytes and specify routing port number
     // auto p = allocDataProtobuf(c);
     meshtastic_MeshPacket *p = router->allocForSending();
+    if (!p)
+        return nullptr;
     p->decoded.portnum = meshtastic_PortNum_ROUTING_APP;
     p->decoded.payload.size =
         pb_encode_to_bytes(p->decoded.payload.bytes, sizeof(p->decoded.payload.bytes), &meshtastic_Routing_msg, &c);

src/mesh/ProtobufModule.h

@@ -44,6 +44,8 @@ template <class T> class ProtobufModule : protected SinglePortModule
     {
         // Update our local node info with our position (even if we don't decide to update anyone else)
         meshtastic_MeshPacket *p = allocDataPacket();
+        if (!p)
+            return nullptr;
 
         p->decoded.payload.size =
             pb_encode_to_bytes(p->decoded.payload.bytes, sizeof(p->decoded.payload.bytes), fields, &payload);

src/mesh/Router.cpp

@@ -194,6 +194,8 @@ PacketId generatePacketId()
 meshtastic_MeshPacket *Router::allocForSending()
 {
     meshtastic_MeshPacket *p = packetPool.allocZeroed();
+    if (!p)
+        return nullptr;
 
     p->which_payload_variant = meshtastic_MeshPacket_decoded_tag; // Assume payload is decoded at start.
     p->from = nodeDB->getNodeNum();

src/mesh/SinglePortModule.h

@@ -32,6 +32,8 @@ class SinglePortModule : public MeshModule
     {
         // Update our local node info with our position (even if we don't decide to update anyone else)
         meshtastic_MeshPacket *p = router->allocForSending();
+        if (!p)
+            return nullptr;
         p->decoded.portnum = ourPortNum;
 
         return p;