Workaround for an error in getting to insert mode.  It was very difficult to reproduce, and I don't know
what led to it, but the ">" mark was set but returned undefined when find() was called.  This should work
around the problem if it happens again.
[vim] Make vim fail more gracefully
[3024-day theme] Change color of matching bracket

The color white is not visible on the current backgroung
[markdown mode] Don't call tokenizer of code-block mode at end of line

Issue #2904
[markdown mode] Support leading whitespace in fencedCodeBlocks mode name
[real-world uses] Add interactive SICP link