mm_assigndirectlib does not open passthrough if library already assigned

[allanbowe]

This is causing a hard to detect error:

</font>MPRINT(POSTDATA.MPE_TARGETLOADER.BITEMPORAL_DATALOADER.DC_ASSIGNLIB):   options metarepository=Foundation;
<strong><font color=red>180: LINE and COLUMN cannot be determined.
</font></strong><font color=blue>NOTE: NOSPOOL is on. Rerunning with OPTION SPOOL might allow recovery of the LINE and COLUMN where the error has occurred.
</font><strong><font color=red>ERROR 180-322: Statement is not valid or it is used out of proper order.

Fix - check for passthrough before returning

%length(&open_passthrough)=0

[github-actions]

🎉 This issue has been resolved in version 4.52.5 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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