To reproduce:
1. Create a new project
2. Create a new HDRP Lit graph
3. Create "Emission Node" and plug it into Lit Master node value
4. Create a "Sample Texture 2D" node
4. Plug "Sample Texture 2D" RGBA(4) value to the Emission node Color(3) value
5. Create two Vector 1 nodes and plug them into Intensity(1) and ExpositionWeight(1)

Expected result: Main Preview shows the default sphere since all the values are default
Actual result: Main Preview window shows only pink checkerboard texture

Reproduced on:
2019.1.0b10 2019.2.0a10

Package version:
-5.3.1
-5.7.2
-5.10.0

Notes:
There is no Emission Node in 5.2.3 or earlier package version for Lit Shader graph
If Intensity(1) or ExpositionWeight(1) are unplugged, the issue disappears.