This bug is very likely caused by one or two corrupted asset files:
Solution (1.11.x and 1.12.x)
This is the solution which should work for 1.11.x and 1.12.x. This may also work for other versions. For a general way to solve this, see "Solution (general)".
Delete the following files and try to start Minecraft again.
To solve this problem you have to do the following:
- Open the index file in the .minecraft\assets\indexes folder of the version which you are trying to play. The file is a normal text file and can be opened with for example Notepad++. The file has probably a name like 1.11.json (for 1.11)
- Search for the two file names listed above
- For each file name do the following:
- Remember the hash value
- Open the .minecraft\assets\objects folder
- Open the folder whose name is the first two letters of the hash value
- Delete the file with the hash value as name
- Try to start Minecraft again
If this did not solve your problem please comment on this report and mention that these steps did not help you.