Remove extra vertical space for any label with no message set

[Override-6]

Hello @zesterer !
There is an issue where the library stills draw extra spaces for labels with no messages, the library still allocate a line regardless if the label has an arrow to display.

This was reported by @kaikalii in #51, adding a check here seems to fix the issue.

ariadne/src/write.rs

Lines 606 to 609 in 8225799

	//No message to draw thus no arrow to draw
	if line_label.label.msg.is_none() {
	continue
	}

however there's still some issues with multiline labels, i need you to determine how this can be handled :

Also, i could'nt find an efficient way to write tests for this PR, thus i allowed myself to add a new example to prove the fix.

other examples

• fixes Labels without messages still create extra vertical space #51

[zesterer]

Thanks so much! Regarding multi-line labels, I've pushed up a commit that should address this. Hopefully with a rebase, this should all work. Let me know when you're ready to merge.

[Override-6]

rebase done