shell: reenable the trace

We now have a couple of protections:
  - if we get close to running out of space in the trace we drop in an
    error
  - if we run out of space in the trace we stop trying to append
  - if there are errors we cancel future evaluations

This is already much nicer. You can't do much on the Mu computer, but at
least it gracefully gives up and shows its limitations. On my computer
the Mu shell tries to run computations for about 20s before giving up.
That seems at the outer limit of what interactivity supports. If things
take too long, test smaller chunks.

1 files changed, 1 insertions, 1 deletions

diff --git a/shell/sandbox.mu b/shell/sandbox.mu
index 944bc88d..1d9e2289 100644
--- a/shell/sandbox.mu
+++ b/shell/sandbox.mu
@@ -29,7 +29,7 @@ fn initialize-sandbox _self: (addr sandbox), screen-and-keyboard?: boolean {
   }
   #
   var trace-ah/eax: (addr handle trace) <- get self, trace
-#?   allocate trace-ah
+  allocate trace-ah
   var trace/eax: (addr trace) <- lookup *trace-ah
   initialize-trace trace, 0x8000/lines, 0x80/visible-lines
   var cursor-in-data?/eax: (addr boolean) <- get self, cursor-in-data?