[WEBJS] - sendImage fails with "msg.avParams is not a function" when sending to Channels (@newsletter)

[Moreno588]

Describe the bug
Sending an image to a WhatsApp Channel (@newsletter JID) via POST /api/sendImage fails with a 500 error. The same image sends successfully to a regular chat (@c.us) with the exact same payload structure.

Version
{
"version": "2026.6.2",
"engine": "WEBJS",
"tier": "CORE",
"browser": "/usr/bin/chromium"
}

Steps to reproduce

1. Connect a WAHA session as admin/owner of a WhatsApp Channel, engine WEBJS, tier CORE.
2. Send POST /api/sendImage with a valid image (tested both via file.url and file.data base64), targeting a channel JID (...@newsletter).
3. Observe the 500 error.

Payload used
{
"session": "default",
"chatId": "XXXXXXXXXXXXXXXXX@newsletter",
"file": {
"url": "https://example.com/image.jpg",
"mimetype": "image/jpeg",
"filename": "banner.jpg"
},
"caption": "test"
}

Error received
{
"statusCode": 500,
"exception": {
"message": "msg.avParams is not a function",
"name": "TypeError",
"stack": "TypeError: msg.avParams is not a function\nwindow.WWebJS.sendMessage (pptr:evaluate;WPage.evaluate (/app/dist/core/engines/webjs/WPage.js:13:36):533:50)\n at window.WWebJS.sendMessage (evaluate at WPage.evaluate (/app/dist/core/engines/webjs/WPage.js:13:36), :532:49)\n at async WebjsClientCore.sendMessage (/app/node_modules/whatsapp-web.js/src/Client.js:1616:25)"
}
}

Additional context

• Tested both with file.url (remote URL) and file.data (base64) — same error in both cases, confirming it's not related to how the media is fetched.
• Sending the same image to a regular chat (@c.us) with the identical payload structure works perfectly (image delivered with caption).
• Sending plain text (POST /api/sendText) to the same channel works fine.
• This appears specific to image messages targeting @newsletter chats in the WEBJS engine.

Full error log

[13:57:03.362] INFO: request errored - POST /api/sendImage - statusCode 500

Error: {
"type": "Error",
"message": "msg.avParams is not a function\nwindow.WWebJS.sendMessage (pptr:evaluate;WPage.evaluate%20(%2Fapp%2Fdist%2Fcore%2Fengines%2Fwebjs%2FWPage.js%3A13%3A36):533:50)",
"stack":
TypeError: msg.avParams is not a function
window.WWebJS.sendMessage (pptr:evaluate;WPage.evaluate%20(%2Fapp%2Fdist%2Fcore%2Fengines%2Fwebjs%2FWPage.js%3A13%3A36):533:50)
at window.WWebJS.sendMessage (evaluate at WPage.evaluate (/app/dist/core/engines/webjs/WPage.js:13:36), :532:49)
at #evaluate (/app/node_modules/puppeteer-core/lib/cjs/puppeteer/cdp/ExecutionContext.js:391:56)
at async ExecutionContext.evaluate (/app/node_modules/puppeteer-core/lib/cjs/puppeteer/cdp/ExecutionContext.js:277:16)
at async IsolatedWorld.evaluate (/app/node_modules/puppeteer-core/lib/cjs/puppeteer/cdp/IsolatedWorld.js:100:16)
at async CdpFrame.evaluate (/app/node_modules/puppeteer-core/lib/cjs/puppeteer/api/Frame.js:362:20)
at async CdpPage.evaluate (/app/node_modules/puppeteer-core/lib/cjs/puppeteer/api/Page.js:818:20)
at async WPage.evaluate (/app/dist/core/engines/webjs/WPage.js:13:20)
at async WebjsClientCore.sendMessage (/app/node_modules/whatsapp-web.js/src/Client.js:1616:25)
at async descriptor.value (/app/dist/core/abc/activity.js:9:20)
"name": "TypeError"
}

Note: identical error reproduced 3 times, testing both file.url (remote URL) and file.data (base64 payload) — same stack trace in all cases.