Cannot invoke "Object.getClass()" because "leftObject" is null

[abhi1693]

Describe the bug
Processor script with tag script_calculate_time_flow_start_ns in pipeline logs-goflow2.sflow-0.1.1 failed with message Cannot invoke "Object.getClass()" because "leftObject" is null

I'm seeing this error when the logs reach elastic index. I'm unable to find relevant code to understand how to fix the error.

To Reproduce
Steps to reproduce the behavior:
Note: I'm seeing this error only when I run with -produce=raw, with -produce=sample no output is generated.

Command: goflow2 -format json -listen "sflow://:6343?queue_size=1" -mapping /etc/goflow2/mapping.yaml -transport.file /var/log/sflow/goflow2/goflow2.log -produce raw

mapping.yaml

# File: /etc/goflow2/mapping.yaml
formatter:
    fields: # list of fields to format in JSON
        - type
        - time_flow_start_ns
        - sampler_address
        - sequence_num
        - in_if
        - out_if
        - src_addr
        - dst_addr
        - etype
        - proto
        - src_port
        - dst_port
        - src_vlan
        - dst_vlan
        - sampling_rate
        - bytes

Expected behavior
To get output without errors using -produce=sample

Captures
If applicable, add output (JSON, protobuf), packet captures and device configuration.

Sampler device:

• Brand: [e.g. Cisco, Juniper, Arista, Mikrotik] Cisco
• Model: [e.g. MX, QFX] NXOS
• Version: [e.g. 22] 9000v
• Estimated flow traffic: [e.g. 5000 samples per second] 20 samples per second

GoFlow2:

• Version: [e.g. v2.0.0] 2.2.1
• Environment: [e.g. Kubernetes, Docker, Debian package] Debian
• OS: [e.g. Linux Ubuntu Server 23.04] Ubuntu 24.04

Additional context
Trying to setup https://www.elastic.co/guide/en/integrations/current/goflow2.html

[lspgn]

Hello @abhi1693,

Thank you for reporting. This looks like an elastic bug.
Could you send me a line of JSON that would trigger the issue?
And/or a packet capture?

[lspgn]

@abhi1693 are you still experiencing the problem? Will close the ticket if I do not hear back

[abhi1693]

You can close the ticket for now. It seems the issue was with using a virtual appliance.

[lspgn]

Thank you :)