[Bug]: Vyper unpacking call's returned values crash Slither

### Describe the issue:

When unpacking the returned values of a call, if multiple values are returned, Slither crashes.

### Code example to reproduce the issue:

```Vyper
# @version 0.3.7

interface X:
def bar() -> (address, address): nonpayable

@internal
def foo(x: X):

a: address = empty(address)
b: address = empty(address)
a, b = x.bar()
```

### Version:

`0.10.1`

### Relevant log output:

```shell
Traceback (most recent call last):
File "/home/csdocker/.local/bin/slither", line 8, in
sys.exit(main())
File "/home/csdocker/.local/share/pipx/venvs/slither-analyzer/lib/python3.10/site-packages/slither/__main__.py", line 746, in main
main_impl(all_detector_classes=detectors, all_printer_classes=printers)
File "/home/csdocker/.local/share/pipx/venvs/slither-analyzer/lib/python3.10/site-packages/slither/__main__.py", line 852, in main_impl
) = process_all(filename, args, detector_classes, printer_classes)
File "/home/csdocker/.local/share/pipx/venvs/slither-analyzer/lib/python3.10/site-packages/slither/__main__.py", line 107, in process_all
) = process_single(compilation, args, detector_classes, printer_classes)
File "/home/csdocker/.local/share/pipx/venvs/slither-analyzer/lib/python3.10/site-packages/slither/__main__.py", line 80, in process_single
slither = Slither(target, ast_format=ast, **vars(args))
File "/home/csdocker/.local/share/pipx/venvs/slither-analyzer/lib/python3.10/site-packages/slither/slither.py", line 150, in __init__
self._init_parsing_and_analyses(kwargs.get("skip_analyze", False))
File "/home/csdocker/.local/share/pipx/venvs/slither-analyzer/lib/python3.10/site-packages/slither/slither.py", line 170, in _init_parsing_and_analyses
raise e
File "/home/csdocker/.local/share/pipx/venvs/slither-analyzer/lib/python3.10/site-packages/slither/slither.py", line 166, in _init_parsing_and_analyses
parser.analyze_contracts()
File "/home/csdocker/.local/share/pipx/venvs/slither-analyzer/lib/python3.10/site-packages/slither/vyper_parsing/vyper_compilation_unit.py", line 63, in analyze_contracts
self._convert_to_slithir()
File "/home/csdocker/.local/share/pipx/venvs/slither-analyzer/lib/python3.10/site-packages/slither/vyper_parsing/vyper_compilation_unit.py", line 73, in _convert_to_slithir
func.generate_slithir_and_analyze()
File "/home/csdocker/.local/share/pipx/venvs/slither-analyzer/lib/python3.10/site-packages/slither/core/declarations/function.py", line 1772, in generate_slithir_and_analyze
node.slithir_generation()
File "/home/csdocker/.local/share/pipx/venvs/slither-analyzer/lib/python3.10/site-packages/slither/core/cfg/node.py", line 717, in slithir_generation
self._irs = convert_expression(expression, self) # type:ignore
File "/home/csdocker/.local/share/pipx/venvs/slither-analyzer/lib/python3.10/site-packages/slither/slithir/convert.py", line 115, in convert_expression
visitor = ExpressionToSlithIR(expression, node)
File "/home/csdocker/.local/share/pipx/venvs/slither-analyzer/lib/python3.10/site-packages/slither/visitors/slithir/expression_to_slithir.py", line 174, in __init__
self._visit_expression(self.expression)
File "/home/csdocker/.local/share/pipx/venvs/slither-analyzer/lib/python3.10/site-packages/slither/visitors/expression/expression.py", line 93, in _visit_expression
self._post_visit(expression)
File "/home/csdocker/.local/share/pipx/venvs/slither-analyzer/lib/python3.10/site-packages/slither/visitors/expression/expression.py", line 267, in _post_visit
self._post_assignement_operation(expression)
File "/home/csdocker/.local/share/pipx/venvs/slither-analyzer/lib/python3.10/site-packages/slither/visitors/slithir/expression_to_slithir.py", line 209, in _post_assignement_operation
assert isinstance(right, TupleVariable)
AssertionError
```