Unhandled error around self.SCHEMA_TYPES

[FedericoCeratto]

Flasgger 0.9.5 seems to raise an empty exception when handling a GET request to an API path (not the documentation page)
The traceback is logged as:

Oct 09 14:57:19 <redacted>[3848779]: ERROR Exception: None
Oct 09 14:57:19 <redacted>[3848779]: ERROR   File "<redacted>/flask/app.py", line 1818, in full_dispatch_request
                                                            rv = self.preprocess_request()
                                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^
                                                          File "<redacted>/flask/app.py", line 2309, in preprocess_request
                                                            rv = self.ensure_sync(before_func)()
                                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                                                          File "<redacted>/base.py", line 677, in before_request
                                                            type=self.SCHEMA_TYPES[
                                                                 ^^^^^^^^^^^^^^^^^^

I suspect the lookup into self.SCHEMA_TYPES at https://github.com/flasgger/flasgger/blob/master/flasgger/base.py#L799 fails.
If wrap the block in a try/except pass the API call runs normally.