[BUG] Temporary preview objects get continuously duplicated

**Describe the bug**
Using Scatter with a custom mesh seems to be duplicating the scattered objects every time you change some parameter of the node group. Not sure which part is causing the problem.

**To Reproduce**
Steps to reproduce the behavior:
1. Download [SorcarBug1.blend.zip](https://github.com/aachman98/Sorcar/files/4718650/SorcarBug1.blend.zip)
2. Change anything on the node group, for example, just changing the Scatter type from "Instanced" to "Instanced" (yeah, the same type) duplicates all objects. Or you can try changing the scale of the generated cube using the transform, then a flurry of objects will be created and never deleted.

**Expected behavior**
Temporary objects should not be created, or at least they should be removed later.

**Desktop (please complete the following information):**
- OS: macOS Mojave
- Blender Version 2.82
- Sorcar Version Master as of today (https://github.com/aachman98/Sorcar/commit/e89bf2db4165f276df2a00137ac722c4c12e8e10)