patch 8.1.1388: errors when calling prop_remove() for an unloaded buffer commit https://github.com/vim/vim/commit/f0884c5f3f5a25481d1e16f0979aa978a6690bb1 Author: Bram Moolenaar <Bram@vim.org> Date: Fri May 24 21:22:29 2019 +0200 patch 8.1.1388: errors when calling prop_remove() for an unloaded buffer Problem: Errors when calling prop_remove() for an unloaded buffer. Solution: Bail out when the buffer is not loaded. Add a few more tests for failing when the buffer number is invalid.