Treating None embeds and views as not having embeds and views in send_message

[TurqW]

Summary

When you call ctx.respond (sending messages, not editing them) and other similar methods, you currently have to put them in an if block to decide whether to include embeds and/or views. With this PR, they'll be able to correctly handle a None, allowing usage of a variable or ternary expression. For instance,

if msg != NO_REMINDERS_MESSAGE:
    view =MyView()
    await ctx.respond(msg, view=view, ephemeral=True)
else:
    await ctx.respond(msg, ephemeral=True)

can now be simplified to:

view = None if msg == NO_REMINDERS_MESSAGE else MyView()
await ctx.respond(msg, view=view, ephemeral=True)

Checklist

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• If type: ignore comments were used, a comment is also left explaining why (N/A)
• This PR fixes an issue. (Debatable)
• This PR adds something new (e.g. new method or parameters). (Debatable)
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, typehinting, examples, ...)

[Dorukyum]

You could pass utils.MISSING but I guess this is also fine.