[BUG] Task fails if empty list is passed as argument

[filippobrizzi]

Describe the bug
Task fails to run if empty list is passed as argument.

Take this task

@flytekit.task
def test_empty_list(
    name: str,
    list_of_stuff: List[str],
) -> int:
    return len(list_of_stuff)

if executed on Flyte (not locally), by passing an empty list to list_of_stuff, it will fail with the following error:

[4/4] currentAttempt done. Last Error: USER::Traceback (most recent call last):
  File "/root/.cache/pypoetry/virtualenvs/flyte-workflows-104TnIye-py3.8/lib/python3.8/site-packages/flytekit/bin/entrypoint.py", line 94, in _dispatch_execute
    outputs = task_def.dispatch_execute(ctx, idl_input_literals)
  File "/root/.cache/pypoetry/virtualenvs/flyte-workflows-104TnIye-py3.8/lib/python3.8/site-packages/flytekit/core/base_task.py", line 402, in dispatch_execute
    native_inputs = TypeEngine.literal_map_to_kwargs(exec_ctx, input_literal_map, self.python_interface.inputs)
  File "/root/.cache/pypoetry/virtualenvs/flyte-workflows-104TnIye-py3.8/lib/python3.8/site-packages/flytekit/core/type_engine.py", line 297, in literal_map_to_kwargs
    return {k: TypeEngine.to_python_value(ctx, lm.literals[k], v) for k, v in python_types.items()}
  File "/root/.cache/pypoetry/virtualenvs/flyte-workflows-104TnIye-py3.8/lib/python3.8/site-packages/flytekit/core/type_engine.py", line 297, in <dictcomp>
    return {k: TypeEngine.to_python_value(ctx, lm.literals[k], v) for k, v in python_types.items()}
  File "/root/.cache/pypoetry/virtualenvs/flyte-workflows-104TnIye-py3.8/lib/python3.8/site-packages/flytekit/core/type_engine.py", line 275, in to_python_value
    return transformer.to_python_value(ctx, lv, expected_python_type)
  File "/root/.cache/pypoetry/virtualenvs/flyte-workflows-104TnIye-py3.8/lib/python3.8/site-packages/flytekit/core/type_engine.py", line 342, in to_python_value
    return [TypeEngine.to_python_value(ctx, x, st) for x in lv.collection.literals]
AttributeError: 'NoneType' object has no attribute 'literals'

Expected behavior
The task should return 0

Screenshots

[fediazgon]

In the latest version is working with empty lists but not with empty dictionaries. I will take a look.