Fail cleanly on non-Object input instead of throwing NullPointerException - #91

Problem

MonetaryAmountDeserializer.deserialize() assumes it is positioned on a START_OBJECT:

while (parser.nextToken() != JsonToken.END_OBJECT) {
    final String field = parser.currentName();

    parser.nextToken();

    if (field.equals(names.getAmount())) {

For any non-Object input, currentName() returns null and the very next line dereferences it. A bare NPE escapes to the caller instead of a JacksonException:

moneta's FastMoney / Money / RoundedMoney deserializers share this class, so they are affected too.

Fix

Check the token up front — the same thing joda-money's MoneyDeserializer already does — and only loop while actually positioned on a PROPERTY_NAME, so malformed content cannot fall into the same trap:

Cannot deserialize value of type `javax.money.MonetaryAmount` from Integer value ...

Also removes a duplicated import javax.money.CurrencyUnit; import javax.money.MonetaryAmount; pair at the top of the file.

Tests

New FailOnNonObjectTest (7 cases): number/string/array/empty-array input, a bad element inside a List<MonetaryAmount>, plus checks that valid Objects and explicit null still deserialize.

javax-money 142 tests and moneta 137 tests all green.