with-nth: Do not trim trailing whitespaces with background colors

Example:
  echo -en '  \e[48;5;232mhello\e[48;5;147m  ' | fzf --ansi --with-nth 1

1 files changed, 3 insertions, 2 deletions

diff --git a/src/util/chars.go b/src/util/chars.go
index e5234303..b1a03fa9 100644
--- a/src/util/chars.go
+++ b/src/util/chars.go
@@ -184,9 +184,10 @@ func (chars *Chars) TrailingWhitespaces() int {
 	return whitespaces
 }
 
-func (chars *Chars) TrimTrailingWhitespaces() {
+func (chars *Chars) TrimTrailingWhitespaces(maxIndex int) {
 	whitespaces := chars.TrailingWhitespaces()
-	chars.slice = chars.slice[0 : len(chars.slice)-whitespaces]
+	end := len(chars.slice) - whitespaces
+	chars.slice = chars.slice[0:Max(end, maxIndex)]
 }
 
 func (chars *Chars) TrimSuffix(runes []rune) {