Debugging projection which reads from non-existing stream throws exception when clicking on Run Step

[shaan1337]

Reproduction steps:

• Create a projection which reads from a stream that does not exist

fromStream('this_stream_does_not_exist')
.when({
    '$any':function(s,e){
       
    }
})

• Click on Debug on the projection page

• Click on Stop

• Click on Run Step

• The following exception will be output in console: TypeError: Cannot read property 'process_event' of undefined