How to reproduce:
1. Open the project "case_1216101-BackwardSlash"
2. Open the Tile Palette window
3. Select "New Palette" in the Tile Palette window
3. Select the Sprites "Square" and "Square 1" in the Project window
4 Drag them into the Tile Palette
5. Select "New Folder" folder when "Generate tiles into folder" window opens
6. Observe the results in the opened "Generate Tile Assets" window

Expected results: the path of the generated asset contains slashes "/" in the opened window
Actual results: the path of the generated asset contains one backward slash "\" in the opened window

Reproducible with: 2017.4.36f1, 2018.4.17f1, 2019.2.20f1, 2019.3.0f6, 2020.1.0a22

Notes:
1. The issue is reproduced only when more than one asset is generated (you can see that in the screenshot "BackwardSlashBugScreenshot2")
2. The issue is reproduced only when the path contains one new created folder, e.g Generating Assets/New Folder/Square.asset (you can see that in the screenshot "BackwardSlashBugScreenshot3")