Operating system: Linux-4.15.0-46-generic-x86_64-with-Ubuntu-18.04-bionic 64 Bits
Graphics card: Radeon RX Vega ATI Technologies Inc. 4.5.13542 Core Profile Context 126.96.36.1998
Broken: version: 2.80 (sub 49)
Worked: Create the inputs at the node_tree level
**Short description of error**
bpy is letting create inputs at the node level for node groups that make blend file unsaveable by crashing blender saving, I think maybe it should throw an error instead, only for node group type of node.
**Exact steps for others to reproduce the error**
1) Go to compositor view
2) Create a group by adding a Mix node and then group it
3) Execute this line in the python console
4) the node now has a new input, but then entering the group the new input is not there
5) save, here it crashes and it doesn't save the file.
The blend file is in step 2)