Allow null values in table

[stephanstapel]

Is your feature request related to a problem? Please describe.
Currently, Spectre.Console throws an exception if one passes a null value for a table cell value:

spectre.console/src/Spectre.Console/Internal/Text/Markup/MarkupParser.cs

Line 7 in 2cc6c45

if (text is null)

Describe the solution you'd like
I propose to get rid of the exception and just assume an empty value (or 'NULL' as an alternative). At least in my environment, I am using Spectre.Console for internal output and am wondering how I would deal with eventual exceptions in my code. Passing a null value is nothing that imho is exceptional, it is just one possible value.

---

Please upvote 👍 this issue if you are interested in it.

[stephanstapel]

I am happy to send in a pull request, just let me know if you want this feature in the component!

[patriksvensson]

Sorry, but why would you create a Markup with a null value? The contract says it accepts a string.

Unless you've turned off nullable reference types, you should get a warning when passing something that might be null. I would recommend doing a value ?? string.Empty in these places.

[stephanstapel]

I'm passing quite values I am adding like

AddRow(Contact?.Firstname, ....);

it would be convenient not to care about null or not null.
I tried ConsoleTableExt which doesn't produce such a nice output but accepts this kind of value.