Allow default option to be overriden if was ocasionally provided on a conversion path

tests/test_default_args.py

@@ -42,6 +42,10 @@ def test_default_consumer_args():
     dep = fn2(123)
     assert dep == (123, '42')
 
+    fn3 = repo.get_conversion((int, optC), consumer, force_commutative=True, force_async=False, allow_async=False)
+    dep = fn3(123, '1')
+    assert dep == (123, '1')
+
 
 def test_default_inj_args():
     repo = ConvRepo()
@@ -68,3 +72,7 @@ def test_default_inj_args():
     fn2 = repo.get_conversion((int,), consumer, force_commutative=True, force_async=False, allow_async=False)
     dep = fn2(123)
     assert dep == 123 + 42
+
+    fn3 = repo.get_conversion((int, optC,), consumer, force_commutative=True, force_async=False, allow_async=False)
+    dep = fn3(123, '0')
+    assert dep == 123