Not sure quite what happened to cause this, sorry. I remember placing a redstone link, setting the frequency, and switching it to receive mode when the game crashed. I can no longer open the world; it crashes after getting past the loading screen for the world. Luckily it was just a creative world and I have everything saved as schematics.
Crash log from first crash: https://paste.ee/p/X3gfQ
Crash log when reopening: https://paste.ee/p/Watpy
World file zip is attached.
world.zip
Sorry I can't provide more information; I'll try to find any other relevant files and put them here.

This issue has been marked as stale because it has been inactive for 3 weeks. It will be closed if it remains inactive for another 3 weeks.

This issue has been closed since it has been inactive for 3 weeks since it was marked as stale.

This should be plenty of information for the devs (crash reports contain a lot of information). It seems it was updating (or powering) a gearshift that caused the crash.
The only other information that might help would be how you placed the gearshift, ie did you use a schematic or quark rotation lock ect.

Your world is recoverable, although possibly not the chunk the gearshift is in. I would be happy to help you recover it if you wanted, even though you have your schematics.

That would be great, thank you! I believe that I placed the gearshift by hand, although it was glued to a bunch of other stuff (encased fan on the bottom, small cog on top, and shafts on the sides). I'm not familiar with the process of recovering a world. Do I need MCEdit for that?

MCEdit doesn't support the new world format that came around in 1.13. Normally there is a forge config option that deletes erroring blocks but that did not work for this case, which is very unfortunate.

There are other tools such as NBTExplorer and MCASelector
I use MCASelector, but you are doing the same thing in NBTExplorer it is just less visual, you have to navigate through the world file tree instead of click and delete.

First you will want to get MCASelector from the GitHub (linked above) and open the jar. Pressing CTRL + O opens file explorer. You will want to navigate to the world you are trying to fix, in this case Create-ive and open the entire world folder.

I have never been able to get the replace specific block function working in it, instructions for doing so are here though, and the the formatting would be 'create:gearshift'=air. If it did work, then it would mean you wouldn't have to delete the entire chunk.
I have tried that your world but it still crashed, so the block was not removed.
Next best option is removing the entire chunk, you do this by left clicking to select the chunk and right clicking to deselect.

The chunk you want to select is -5, -13 as stated here in your crash report

	Block: Block{create:encased_fan}[facing=down]
	Block location: World: (-68,13,-203), Chunk: (at 12,0,5 in -5,-13; contains blocks -80,0,-208 to -65,255,-193), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)

You then go to the menu at the top and Selection > Delete selected chunks

It will autosave and your world is good to open again! (minus the problematic chunk, of course)
Your file should end up something like this (this is one I have done, if you don't want to follow the steps above or something goes wrong): World.zip

Thank you so much! I'll be sure to do this if I run into this issue again. I think the cause of the crash may have been the redstone link and not the gearshift, but I'm not sure. I'll look into it a bit more.