Verify your GG installation after every update.
This is important and could be the reason for editor, test mode or standalone game crashes.
I had 148 missing/corrupted files at the first check, 2nd check still 12 files missing, 3rd check was ok.
And voila, the new created standalone game was not crashing anymore and the ground texture was correct.
I've another standalone game, I'll test it tonight.... But I know already, that the textures from some buildings are missing (building pack, please fix that).
How to verify your GG installation:
Go to steam
Go to your software lib
Right click on the GG icon
Go to properties
Go to the 3rd tab
Click on verify installation (not 100% sure what's written there in English, as my steam language is German)
Now steam will check your installation and download missing files.
At the end click again one more time on verify, to be sure that everything is alright now.
Note: keep in mind, that the verify will replace your custom sounds, gfx and everything you edited and set it back to default. If you've edited the zombie sounds, after the verify they will be back to default. Same for custom background menu gfx, if you saved them in the default folder.
Old school FPS fan, DOOM!!! Why GG not working on my AMIGA 500?