A minimum tactical fix for issue #697

[SteveGilham]

Terminate the iteration if it steps on to a null Instruction to allow for uninitialized trailing cells in the case of size less than capacity.

[jbevain]

Hello @SteveGilham,

Thank for the PR! Could add a unit test to the test suite from your repro before I merge? Thanks!

Jb

[SteveGilham]

The test does a little more manipulation than the plain "it blows up" repro to

1. match the full use case in which the issue arose
2. get to an end state that is simple to assert

I don't know if there's a more elegant way in the infrastructure to get at the assembly -- the code in the module tests to load an assembly and do tests seemed to do more than required by way of repeating all symbol reading combinations.

[jbevain]

Thank you!