Describe the bug

Error: header name must be a non-empty string is thrown we coping empty headers object

I suspect set method of AxiosHeaders do not detect instance properly

Given a code

import {AxiosHeaders} from "axios";
const axios = require('axios');

new AxiosHeaders(new axios.AxiosHeaders());

Expected: empty headers created
Actual: header name must be a non-empty string error thrown

To Reproduce

Please run the code below to reproduce, I tested on 1.8.x and 1.7.x versions

Code snippet

import {AxiosHeaders} from "axios";
const axios = require('axios');

new AxiosHeaders(new axios.AxiosHeaders());

Run the code

esbuild reproduce.ts --bundle --platform=node | node

Expected behavior

an empty headers object created

Actual behavior

Error: header name must be a non-empty string
    at setHeader ([stdin]:15089:15)
    at AxiosHeaders.set ([stdin]:15106:25)
    at new AxiosHeaders ([stdin]:15082:21)
    at [stdin]:17352:1
    at runScriptInThisContext (node:internal/vm:209:10)
    at node:internal/process/execution:118:14
    at [stdin]-wrapper:6:24
    at runScript (node:internal/process/execution:101:62)
    at evalScript (node:internal/process/execution:133:3)
    at node:internal/main/eval_stdin:32:5

Node.js v20.17.0

Axios Version

1.8.3

Adapter Version

No response

Browser

No response

Browser Version

No response

Node.js Version

20.x

OS

OSx 15.3.2

Additional Library Versions

Additional context/Screenshots