Optimize array serialization by not serializing null range

[nowol]

If we have an array with the following content

[0] = a
[1] =
[2] = c
[3] =
[4] =
[5] =

we could change the payload of the array to something like this:
| |

This way we do not have to serialize empty/null entries. This can be important for List<> where they use a simple 'double' algorithm for their array.