exceptions during drawing processes are discarded

[masuhar]

The exception handler in update.js:152

• catches exceptions not only the ones raised in eval, but also the ones raised in the subsequent processes, such as graph drawing, but
• only reports 'infinite loop' cases; i.e., silently discards other exceptions.

This makes it very difficult to spot bugs in the Kanon runtime. For example, an attempt to modify a visjs' graph mistakenly creates 'undefined' entry in a graph.edges, which causes an exception in the subsequent process. However, Kanon simply displays a graph before modifying the graph.

This should also be bad for exceptions in the user program.

[masuhar]

https://cws-prg.slack.com/archives/C06K1PMLKD3/p1727324180000979?thread_ts=1727317468.625599&cid=C06K1PMLKD3