The problem with the adding GPU Instancing for shader

Hello,
We need to use TreeSoftOcclusionLeaves (it is build in shader). And we need it with GPU Instancing to increase FPS. Original shader doesn't have GPU Instancing.
I added the line "#pragma multi_compile_instancing" and now i see that batching is working when i have objects (bushes) on scene. But when i draw those objects on the terrain the batching stop working.
Also i found that if delete the "#pragma fragment frag" then the batching start working even if the objects on terrain. I suppose i need to write something into "fixed4 frag(v2f input) : SV_Target" to made GPU Instancing works fine but i don't know what.


Thank you in advance for any help!