[Simple-support] @Attribute (empty = "-1", required = false) seams not to work

[-=}\\*/{=- <rui...@gm...>]

  @Attribute (empty = "1", required = false)
  int debugLevel = -1;

gives the following error:

Exception in thread "main" java.lang.IllegalArgumentException: Can not set
int field abc.kis.Context.debugLevel to java.lang.String
 at
sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:164)
at
sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:168)
 at
sun.reflect.UnsafeIntegerFieldAccessorImpl.set(UnsafeIntegerFieldAccessorImpl.java:98)
at java.lang.reflect.Field.set(Field.java:675)
 at org.simpleframework.xml.core.FieldContact.set(FieldContact.java:212)
at org.simpleframework.xml.core.Collector.commit(Collector.java:169)
 at org.simpleframework.xml.core.Composite.readDefault(Composite.java:263)
at org.simpleframework.xml.core.Composite.read(Composite.java:232)

....

also tried with positive number.