Zero width cubes results in invalid models

**Issue**
When making a Blockbench model, setting a cube to `0` width in any of the axis will result the plugin to generate models with `null` in the bones. This causes the model to be invalid.

**Expectations**
When creating a `0` width cube, the plugin should generate `0` in the bones.

**Actual**
When creating a `0` width cube, the plugin generates `null` in the bones.