IndexError: pop from empty list

[pintman@…]

How to Reproduce

While doing a GET operation on /attachment/wiki/Eigenes Projekt/, Trac issued an internal error.

The problem only occurs when an attachment is about to be uploaded to a wiki page or a ticket after clicking the "add attachment" button. But only when German is selected as language. When using english as default language everything works fine.

Request parameters:

{u'action': u'new', 'path': u'Eigenes Projekt/', 'realm': u'wiki'}

User agent: Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:48.0) Gecko/20100101 Firefox/48.0

System Information

Trac	1.0.13
Babel	2.3.4
Genshi	0.7 (without speedups)
pysqlite	2.6.0
Python	2.7.6 (default, Jun 22 2015, 18:00:18) [GCC 4.8.2]
pytz	2016.7
setuptools	3.3
SQLite	3.8.2
jQuery	1.7.2
jQuery UI	1.8.21
jQuery Timepicker	1.0.1

Enabled Plugins

Python Traceback

Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/trac/web/main.py", line 562, in _dispatch_request
    dispatcher.dispatch(req)
  File "/usr/local/lib/python2.7/dist-packages/trac/web/main.py", line 269, in dispatch
    iterable=chrome.use_chunked_encoding)
  File "/usr/local/lib/python2.7/dist-packages/trac/web/chrome.py", line 1115, in render_template
    encoding='utf-8')
  File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 184, in render
    return encode(generator, method=method, encoding=encoding, out=out)
  File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 58, in encode
    for chunk in iterator:
  File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 350, in __call__
    for kind, data, pos in stream:
  File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 829, in __call__
    for kind, data, pos in stream:
  File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 669, in __call__
    for kind, data, pos in stream:
  File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 774, in __call__
    for kind, data, pos in chain(stream, [(None, None, None)]):
  File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 594, in __call__
    for ev in stream:
  File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure
    for event in stream:
  File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure
    for event in stream:
  File "/usr/local/lib/python2.7/dist-packages/trac/web/chrome.py", line 1321, in _strip_accesskeys
    for kind, data, pos in stream:
  File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure
    for event in stream:
  File "/usr/local/lib/python2.7/dist-packages/trac/web/chrome.py", line 1310, in _generate
    for kind, data, pos in stream:
  File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include
    for event in stream:
  File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 378, in _match
    ctxt, start=idx + 1, **vars):
  File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 378, in _match
    ctxt, start=idx + 1, **vars):
  File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 326, in _match
    for event in stream:
  File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 558, in _flatten
    for kind, data, pos in stream:
  File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure
    for event in stream:
  File "/usr/local/lib/python2.7/dist-packages/genshi/path.py", line 588, in _generate
    subevent = next()
  File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include
    for event in stream:
  File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 315, in _strip
    event = next()
  File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 558, in _flatten
    for kind, data, pos in stream:
  File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure
    for event in stream:
  File "/usr/local/lib/python2.7/dist-packages/genshi/path.py", line 588, in _generate
    subevent = next()
  File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include
    for event in stream:
  File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 315, in _strip
    event = next()
  File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 558, in _flatten
    for kind, data, pos in stream:
  File "/usr/local/lib/python2.7/dist-packages/genshi/filters/i18n.py", line 178, in _generate
    for event in msgbuf.translate(gettext(msgbuf.format())):
  File "/usr/local/lib/python2.7/dist-packages/genshi/filters/i18n.py", line 1051, in translate
    events = self.events[order].pop(0)
IndexError: pop from empty list