You can empty the trash from the command line. Follow these instructions
exactly and double-check each command to ensure you are doing the right thing in the right place.
Open up a Terminal windows (Applications->Utilities->Terminal) and enter the following command
Now, confirm you are in the right place with
This should give you a response like
/Users/<username>/.Trash. If that isn't the case,
DO NOT CONTINUE! Close the terminal with CMD+q and go back to step 1 above and restart. Ignoring this will have dire consequences and you've been warned.
If the response was correct, then do
This will list the contents of the folder sorted by the largest files first and only show you about 9 or so files.
You are now ready to delete the first file in the list since it is the largest file. Do so with
Enter the name of the file as you listed (copy and paste if it helps) to remove it. If the name has spaces in it, you will find it easier to put it between double quotes to avoid issues.
Once you've deleted the first file, confirm by using the command
ls -lS | head again. The file you deleted shouldn't show up anymore.
Now try to empty the trash using the UI. If it complains, remove the next largest file from the Terminal, rinse and repeat until the UI starts to function.
The MBA traditionally has either 128GB or 256GB of storage and it's easy to fill things up. For nominal macOS operation you should leave 20% of the disk free at all times, so in the future pay attention to your free space.