fixed #2429 Previewing a world breaks world preview for remainder of game session

[0shine0]

Contains

Fixes #2429 and partially fixes #2509

How to test

For issue 2429

1. Click on Single Player > Create > Details
2. Wait for screen to show up
3. Then click on Back
4. Click on Details again
5. It shows null pointer exception and preview does not load
6. Can be tested by selecting any world generator or module(even stable ones will show this exception)

For issue 2509

The 1st problem is not yet tackled but the reason for lag is the setting the environment which causes the assets to reload and when back button is pressed the environment is reset which also causes assets to reload and hence I think the lag

The 2nd problem in this issue is actually the above issue which is fixed

The 3rd problem is tackled in the commit for issue 2509 in which the game crashes or will be needed process killed.

1. Click on Single Player > Create > Details
2. Wait for screen to show up
3. Then click on Back
4. Click on Back again
5. Click on Create
6. The game crashes showing a null pointer exception
   Note: The 2nd and 3rd problem imployed the same solution as the problem was same that the variables(with @it above them) that referenced to Core Registry for values were set to null.

I don't think the fourth problem is actually because of preview Class. The null pointer exception in this case is due to world i.e. what we get from worldGenerator.getWorld() being null and further use of world variable causes null pointer exception. I think the problem in this case is with the world creation procedure in this specific module because the world is not even fully loaded when the player is spawned in the game.

PS: solved the tta preview problem. Now it opens preview but does not show anything as its preview functionality is not defined. I think that should be made into another issue and this issue should be closed.
pr 3 in ClimateConditions and pr from new branch 'shine1' in WoodAndStone are made for this issue

[GooeyHub]

Can one of the admins please verify this patch?

[Cervator]

Thanks for this @0shine0 !

@flo @msteiger either of you interested in checking this one out? If not I'll try to catch it over the weekend

@GooeyHub: add to whitelist

[GooeyHub]

Hooray Jenkins reported success with all tests good!

[GooeyHub]

Hooray Jenkins reported success with all tests good!

[0shine0]

@Cervator Please test and review the changes. Solved the issue.

[GooeyHub]

Hooray Jenkins reported success with all tests good!

[Cervator]

Tested out and merged!

I saw the two module PRs and left some comments there, still need to merge those.

I'm adding some more notes on what's left in the GSOC scope #2774 - that way we can let the two associated issues to this count as being fixed :-)