It makes sense: your input is not really a date because it does not have a day information. You should parse it as a YearMonth and use that result if you don’t care about the day.
String date = "04.2013";
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MM.yyyy");
YearMonth ym = YearMonth.parse(date, formatter);
If you do need to apply a specific day, you can obtain a LocalDate from a YearMonth for example:
LocalDate ld = ym.atDay(1);
//or
LocalDate ld = ym.atEndOfMonth();
You can also use a TemporalAdjuster, for example, for the last day of the month*:
LocalDate ld = ym.atDay(1).with(lastDayOfMonth());
*with an import static java.time.temporal.TemporalAdjusters.lastDayOfMonth;