A safer way to cut a string
Here's my take on it:

def getFirstParagraph(txt: String): String = txt.lines.next


As to the null objection: in idiomatic Scala, you don't use null. If there's some API which might return you a null string, then, at that point, you turn it into an Option, and handle the Option elsewhere as needed.

Handling null (or even Option) at the getFirstParagraph method is misplaced.