Fit addon fails to propose correct dimenions

This issue came up when I tried to update from xterm 5.0.0 to 5.1.0. xterm-addon-fit is the same version 0.6.0

First the fit() method as called before does not work and upon some debugging, proposeDimensions() always returns Object { cols: NaN, rows: NaN }

Unfortunately I have no clue how to debug this further as stepping through the function with the debugger and sourcemaps mostly shows undefined objects and skips lines and I don’t know how to build the assets correctly from the .ts files if I’d want to add some console.log()s.

There are some suspicious comments like https://github.com/xtermjs/xterm.js/blob/master/addons/xterm-addon-fit/src/FitAddon.ts#L60 which may hint at the issue?

Details

• Browser and browser version: both current ff and chrome
• xterm.js version: 5.1.0

Steps to reproduce

The code is essentially just the example code from the addon Readme and it used to work.