The map that I've downloaded is not fully generated and I can only see half of it

I have this problem when trying to play a world that I have on a current version that hasn't been played since 0.11.1. Doesn't matter if this version is a client looking at its local worlds (in the "games/com.mojang/" folder for the actual game) or as a server. I think it's just the way they changed the format levels are saved in 1.2.

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Thank you for your report!
However, this issue is Incomplete.

Your report does not contain enough information. As such, we're unable to understand or reproduce the problem.

Please review the guidelines linked below before making further reports.

Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – 📖 Game Wiki

Thank you for your report!
However, this issue is Incomplete.

Your report does not contain enough information. As such, we're unable to understand or reproduce the problem.

Please review the guidelines linked below before making further reports.

Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – 📖 Game Wiki