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/modules/StatusMessageModule.cpp

@@ -15,6 +15,8 @@ int32_t StatusMessageModule::runOnce()
         strncpy(ourStatus.status, moduleConfig.statusmessage.node_status, sizeof(ourStatus.status));
         ourStatus.status[sizeof(ourStatus.status) - 1] = '\0'; // ensure null termination
         meshtastic_MeshPacket *p = allocDataPacket();
+        if (!p)
+            return 1000 * 12 * 60 * 60;
         p->decoded.payload.size = pb_encode_to_bytes(p->decoded.payload.bytes, sizeof(p->decoded.payload.bytes),
                                                      meshtastic_StatusMessage_fields, &ourStatus);
         p->to = NODENUM_BROADCAST;