fix issue with negative available per validator

[joe-bowman]

1. Summary

• add guards against negative completion times (should not be possible now, but belt and braces)
• panic (hooks and tx, so safe) on negative allocations
• fixes a test that no longer generates an error, given no satisfiable unbondings
• adds a check on msgResponseType if its not empty string then 46 otherwise 45

2.Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

3. Implementation details

Add guards against invalid completion times.
Panic on negative unbonding allocation.

[ajansari95]

Closes comments from #313 for table based check and closes the PR

[joe-bowman]

Minor bits but otherwise good

[ajansari95]

LGTM