Infinite loading on error in dyne-slangroom-editor

[matteo-cristino]

When a runtime slangroom error happens the slangroom editor start an infinite loading instead of reporting the error.

Step to reproduce:

1. visit https://dyne.org/slangroom/playground/
2. use as contract:

   Prepare 'res': manipulate and get where object is 'obj', path is 'path'
   Given I have a 'string' named 'res'
   Then print the data

3. use as keys:

   {
       "obj": {
           "a": "b"
       },
       "path": "c"
   }

4. press execute contract

result: