Not entirely sure whats going on here, but why not just put the limit in here

Instead of `defaultLimit`:
```
limit = Settings.mmsSizeLimitation * 0.9;
```

and then later

```
if (!limit || blob.size < limit) {
  callback(blob);
} else {
.....
`

If you were trying to force there to ALWAYS be a limit, that doesn't seem necessary, the key will be set in the settings yes?