Make defaults delete more robust

Author: ychin

.github/workflows/macvim-buildtest.yaml

@@ -368,7 +368,7 @@ jobs:
         if: startsWith(github.ref, 'refs/tags/') || !inputs.testgui
         timeout-minutes: 30
         run: |
-          defaults delete org.vim.MacVim  # Clean up stale states
+          defaults delete org.vim.MacVim || true  # Clean up stale states
           # Currently we don't run any non-src tests, as syntax tests are fragile and prone to spamming escape codes.
           # This needs to be investigated and fixed upstream.
           # MacVim is unlikely to introduce breaking changes in runtime files anyway.