vis-complete: handle non-ascii text

The '[:alnum:]' set does not include non-ascii text which results in
the non-ascii text being replaced with newlines. Using the '[:blank:]'
set with no complement flag fixes this issue.

vis-complete

@@ -48,7 +48,7 @@ fi
 PATTERN="$1"
 
 if [ $COMPLETE_WORD = 1 ]; then
-	tr -cs '[:alnum:]_' '\n' |
+	tr -s '[:blank:]_' '\n' |
 		grep "^$(basic_regex_quote "$PATTERN")." |
 		sort -u
 else