Editor: Add element to empty array of materials leads to crash

## Description

Add element to empty array of materials leads to crash

## Steps to Reproduce

1. Create an object with mesh
2. Remove all materials with "-" button
3. Add new one with "+"

### Expected behavior:

3. Material added

### Actual behavior:

3. Application crashed

### Reproducibility:

100%

## Versions

2023.3

## Additional Information

n/a
