Placing a section at the end of montage is not properly handled

Placing a  section at the very end of a montage with no duration or animation assigned after it is not properly handled. 

Normally sections with 0 length are skipped and search continues since they do not pass the check for UAnimMontage::IsWithinPos(), ** this is true for all cases except if the montage section is at the end (since the search passes before continuing reaching the last section).

Therefore this causes issues when querying the current section and/or breaks a montage loop determined by linking sections together since the last section is never reached.

Therefore we need to either issue a warning when placing a section at the very end or properly handle that edge case.

• Open an animation montage with various sections in it
• Ensure these section linkage is ordered based on section's start time
• Place a section at the very end of a montage with no duration or animation assigned after it
• Make the last section loop back to the first section
• Play and see how the montage never loops