Invalid memory access in pg_stat_get_subscription

Hello hackers,

While exploring some code in logical replication worker
implementation, I noticed that we're accessing an invalid memory while
traversing LogicalRepCtx->workers[i].
For the above structure, we're allocating
max_logical_replication_workers times LogicalRepWorker amount of
memory in ApplyLauncherShmemSize. But, in the for loop, we're
accessing the max_logical_replication_workers + 1 location which is
resulting in random crashes.

Please find the patch that fixes the issue. I'm not sure whether we
should add a regression test for the same.

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Thanks & Regards,
Kuntal Ghosh