[BUG] Cannot create Groups if there are links going in or out of the new Group.

**Describe the bug**
Creating Node Groups doesn't work in Blender 3.0.0+

**To Reproduce**
Create a few Sorcar nodes and connect them together in a sensible way.
(I used a Bool node and an If-Else node and some other node.)
Try and create a group with some links going in or out.
Notice how the node groups cannot create links for sockets created by Sorcar,
but it seems socket classes from the bpy.types built-ins work just fine.
Try a few different kinds of links.

**Expected behavior**
The node group is created and linked.

**Screenshots**
If applicable, add screenshots to help explain your problem.

**Desktop (please complete the following information):**
- OS: Manjaro GNU/Linux
- Blender Version 3.0
- Sorcar Version master branch hash: 650cb6585c3f8a92af029ae7f5c2d7453e9459ef

**Additional context**
Terminal output:
```
Error: Python: Traceback (most recent call last):
File "/home/joseph/.config/blender/3.0/scripts/addons/Sorcar-master/operators/ScGroupNodes.py", line 97, in execute
node_tree.links.new(group_node.outputs[i], link.to_node.inputs[link.to_socket.name])
IndexError: bpy_prop_collection[index]: index 0 out of range, size 0

location: :-1

Error: Python: Traceback (most recent call last):
File "/home/joseph/.config/blender/3.0/scripts/addons/Sorc
[sorcar_bug.blend.zip](https://github.com/aachman98/Sorcar/files/7841231/sorcar_bug.blend.zip)
ar-master/operators/ScGroupNodes.py", line 94, in execute
node_tree.links.new(link.from_node.outputs[link.from_socket.name], group_node.inputs[i])
IndexError: bpy_prop_collection[index]: index 0 out of range, size 0

location: :-1

Error: Python: Traceback (most recent call last):
File "/home/joseph/.config/blender/3.0/scripts/addons/Sorcar-master/operators/ScGroupNodes.py", line 94, in execute
node_tree.links.new(link.from_node.outputs[link.from_socket.name], group_node.inputs[i])
IndexError: bpy_prop_collection[index]: index 0 out of range, size 0

location: :-1
```
File Attached.

My guess is that the Blender devs added a well-meaning poll function to the builtin Group node... but it breaks Sorcar, and since *my addon* is using your wonderful Create Group operator as a template, mine is broken, too!
Anyhow I think the solution is to create your own custom NodeGroupIn or Out nodes, or find a way to overwrite the builtin nodes poll() method.

I don't use Sorcar myself, but since I am borrowing your code, I wanted to pass this on. I'll try to keep you updated with my own solution to the problem.