How do I get rid of 1.5 line spaces in gmail?

If you are composing an email in gmail on chrome and hit shift-enter it makes a single new line. If you hit enter it makes 1.5 new lines of whitespace. However, after I make 1.5 new lines of whitespace I cannot delete them! If I combine two lines one before and one after the 1.5 lines of white space then the single spaced line below becomes 1.5 spaced. AARRRGGG!!!!! I feel like Microsoft-auto-correct somehow snuck into gmail.