Yarp: Negative VOCAB in Image.h

[drdanz]

As noticed by @jgvictores (https://github.com/robotology/yarp/commit/185a9c36334860c5f655cf25b3766a7c680cf215#r29116913) there is a negative VOCAB in Image.h

https://github.com/robotology/yarp/blob/185a9c36334860c5f655cf25b3766a7c680cf215/src/libYARP_sig/include/yarp/sig/Image.h#L63-L65

@aerydna is this wanted or just a typo?

[Nicogene]

I checked and it is there since yarp 2.3.65 :scream:
But I think it was a typo.
@barbalberto what do you think about?

[barbalberto]

Negative pixelsize were allowed for "custom weird types", but negative VOCAB does not make sense to me.
I agree, probably that's a typo.

[jgvictores]

Yes, it seems it was introduced way back at 0a193e5... only issue here is that the fix definitely breaks b/w compat.

[Nicogene]

@lornat75 the negative vocab introduced here 0a193e5 is intentional or a leftover ?