Mongo Query Not Generating Boolean Value

**Describe the bug**
I am using the Vue cube.js client and I am using Mongo BI Connector as my datasource.

I have a boolean dimension in one of my cubes, but when I execute a query I get the following SQL generated:

```
SELECT * FROM `cube` WHERE (`cube.myBoolean` <> 'true'
OR `cube.myBoolean` IS NULL);
```

Note how the value it is comparing against is `'true'` and not `true`.

**Expected behavior**
I expect it to generate something like:

```
SELECT * FROM `cube` WHERE (`cube.myBoolean` <> true
OR `cube.myBoolean` IS NULL);
```

**Version:**
0.21.1

**Additional context**
This is a huge issue for me because my MongoDB has an index on that field, and this causes my index to not work. Is there any temporary workaround I can do until this gets fixed?