How to reproduce:
1. Open the attached '1229053.zip' project
2. Open 'samplescene' Scene
3. Enter Play Mode
4. Select 'Copy Texture' GameObject in the Hierarchy
5. Double click Light Buffer's RenderTexture in the Inspector
6. Notice that Render Texture inspector displays the current contents of Render Texture based on Camera's output
7. Open 'CopyTexture.cs' script and comment 25th line
8. Re-enter Play Mode
9. Double click Light Buffer's RenderTexture in the Inspector

Expected result: Render Texture inspector displays the current contents of Render Texture based on Camera's output
Actual result: Render texture is white

Reproducible with: 2019.3.7f1(7.1.8), 2020.1.0b3(8.0.1), 2020.2.0a4(8.0.1)
Could not test with: 2017.4.38f1 because Package Manager is not introduced, 2018.4.19f1 due to errors thrown to the Console

Notes:
- Video and project of reproduction attached in Edit
- Not reproducible with Tex2D type