circulation: unable to display a patron account in public view when he has a dispute.

[benerken]

Describe the bug
The issue occurs in the public view, when the patron is logged and he wants to access its profile.
If he has a "dispute" transaction in the history of fees, he gets an internal server error on the screen.

The server logs shows this kind of message:

File "/invenio/.cache/pypoetry/virtualenvs/rero-ils-Ta2-9VdS-py3.6/lib/python3.6/site-packages/jinja2/runtime.py", line 679, in _invoke
rv = self._func(*arguments)
File "/invenio/src/rero_ils/modules/patrons/templates/rero_ils/_macro_profile.html", line 123, in template
{{ event.amount | format_currency(event.currency) }}
File "./rero_ils/modules/patrons/views.py", line 238, in format_currency_filter
return format_currency(value, currency)
File "/invenio/.cache/pypoetry/virtualenvs/rero-ils-Ta2-9VdS-py3.6/lib/python3.6/site-packages/flask_babelex/init.py", line 444, in format_currency
number, currency, format=format, locale=locale
File "/invenio/.cache/pypoetry/virtualenvs/rero-ils-Ta2-9VdS-py3.6/lib/python3.6/site-packages/babel/numbers.py", line 521, in format_currency
decimal_quantization=decimal_quantization)
File "/invenio/.cache/pypoetry/virtualenvs/rero-ils-Ta2-9VdS-py3.6/lib/python3.6/site-packages/babel/numbers.py", line 943, in apply
value = decimal.Decimal(str(value))
decimal.InvalidOperation: [<class 'decimal.ConversionSyntax'>]

To Reproduce

1. Go to ilsdev.test.rero.ch
2. login as Astrid and go to the professional interface.
3. Take the account of Simonetta, Tabs "Fees" and do a dispute for an open fee
4. Logout, then login as Simonetta
5. In the public view, try to access the patron profie. You should get an Internal Server Error.

Expected behavior
A patron with fees (and dispute) should be able to display its profile.

Context
Tell us on what server did you spotted the issue, using with browser.

• server: ilsdev.test.rero.ch
• version: 0.12