setting a payload metric to null should throw an exception immediately

[pstanton]

If you set a metric to null:

KuraPayload.addMetric("xyz", null);

The payload is a ticking time bomb and will throw an exception when it is encoded later:

org.eclipse.kura.KuraInvalidMetricTypeException: Metric null value is invalid.
        at org.eclipse.kura.core.cloud.CloudPayloadProtoBufEncoderImpl.setProtoKuraMetricValue(CloudPayloadProtoBufEncoderImpl.java:166)
        at org.eclipse.kura.core.cloud.CloudPayloadProtoBufEncoderImpl.getBytes(CloudPayloadProtoBufEncoderImpl.java:66)

It should either:
a) be skipped when encoding later (ignored)
b) throw an exception on the 'addMetric' call

[cdealti]

@pstanton thanks. Maybe a) would be the preferred option. Option b) would require an unchecked exception for API backward compatibility and these exceptions are dangerous.

Are you going to submit a pull request?

Ciao,
Cristiano