There are two ways to remove the empty lines in notepad ++. First option we can use regular expression to replace  and the second option using Line operation provided by Notepad ++. Lets say i have lot of empty lines in my notepad as like below

Option 1:

We can use the regular expression to replace all the empty lines, Click on Control+F in notepad and go to replace tab.In find what field type '\n\r' and Replace field should be kept blank then click replace all button.

Output:

Option 2:

These are the two ways we can remove the empty lines in notepad++.