# Buggy code
def _resolve_buffer_index(self, index):
    """Resolve a buffer index to the tabbedbrowser and tab.

    Args:
        index: The [win_id/]index of the tab to be selected. Or a substring
               in which case the closest match will be focused.
    """
    index_parts = index.split("/", 1)

    try:
        for part in index_parts:
            int(part)
    except ValueError:
        model = miscmodels.buffer()
        model.set_pattern(index)
        if model.count() > 0:
            index = model.data(model.first_item())
            index_parts = index.split("/", 1)
        else:
            raise cmdexc.CommandError("No matching tab for: {}".format(index))

    if len(index_parts) == 2:
        win_id = int(index_parts[0])
        idx = int(index_parts[1])
    elif len(index_parts) == 1:
        idx = int(index_parts[0])
        active_win = objreg.get("app").activeWindow()
        if active_win is None:
            # Not sure how you enter a command without an active window...
            raise cmdexc.CommandError(
                "No window specified and couldn't find active window!"
            )
        win_id = active_win.win_id

    if win_id not in objreg.window_registry:
        raise cmdexc.CommandError("There's no window with id {}!".format(win_id))

    tabbed_browser = objreg.get("tabbed-browser", scope="window", window=win_id)
    if not 0 < idx <= tabbed_browser.count():
        raise cmdexc.CommandError("There's no tab with index {}!".format(idx))

    return (tabbed_browser, tabbed_browser.widget(idx - 1))


# Traceback (ValueError)
16:39:44 DEBUG    init       app:_init_modules:468 Initializing websettings...
16:39:45 ERROR    misc       crashsignal:exception_hook:216 Uncaught exception
Traceback (most recent call last):
File "/bin/qutebrowser", line 11, in <module>
load_entry_point('qutebrowser==1.1.1', 'gui_scripts', 'qutebrowser')()
File "/usr/lib/python3.6/site-packages/qutebrowser/qutebrowser.py", line 188, in main
return app.run(args)
File "/usr/lib/python3.6/site-packages/qutebrowser/app.py", line 137, in run
init(args, crash_handler)
File "/usr/lib/python3.6/site-packages/qutebrowser/app.py", line 163, in init
_init_modules(args, crash_handler)
File "/usr/lib/python3.6/site-packages/qutebrowser/app.py", line 469, in _init_modules
websettings.init(args)
File "/usr/lib/python3.6/site-packages/qutebrowser/config/websettings.py", line 215, in init
webenginesettings.init(args)
File "/usr/lib/python3.6/site-packages/qutebrowser/browser/webengine/webenginesettings.py", line 297, in init
websettings.init_mappings(MAPPINGS)
File "/usr/lib/python3.6/site-packages/qutebrowser/config/websettings.py", line 198, in init_mappings
mapping.set(value)
File "/usr/lib/python3.6/site-packages/qutebrowser/config/websettings.py", line 72, in set
self._set(value, settings=settings)
File "/usr/lib/python3.6/site-packages/qutebrowser/browser/webengine/webenginesettings.py", line 154, in _set
filenames = [self._find_installed(code) for code in value]
File "/usr/lib/python3.6/site-packages/qutebrowser/browser/webengine/webenginesettings.py", line 154, in <listcomp>
filenames = [self._find_installed(code) for code in value]
File "/usr/lib/python3.6/site-packages/qutebrowser/browser/webengine/webenginesettings.py", line 143, in _find_installed
local_filename = spell.local_filename(code)
File "/usr/lib/python3.6/site-packages/qutebrowser/browser/webengine/spell.py", line 64, in local_filename
all_installed = local_files(code)
File "/usr/lib/python3.6/site-packages/qutebrowser/browser/webengine/spell.py", line 51, in local_files
for matching_dict in sorted(matching_dicts, key=version, reverse=True):
File "/usr/lib/python3.6/site-packages/qutebrowser/browser/webengine/spell.py", line 36, in version
.format(filename))
ValueError: the given dictionary file name is malformed: /usr/share/qt/qtwebengine_dictionaries/en-US.bdic

# Fixed code
def _resolve_buffer_index(self, index):
    """Resolve a buffer index to the tabbedbrowser and tab.

    Args:
        index: The [win_id/]index of the tab to be selected. Or a substring
               in which case the closest match will be focused.
    """
    index_parts = index.split("/", 1)

    try:
        for part in index_parts:
            int(part)
    except ValueError:
        model = miscmodels.buffer()
        model.set_pattern(index)
        if model.count() > 0:
            index = model.data(model.first_item())
            index_parts = index.split("/", 1)
        else:
            raise cmdexc.CommandError("No matching tab for: {}".format(index))

    if len(index_parts) == 2:
        win_id = int(index_parts[0])
        idx = int(index_parts[1])
    elif len(index_parts) == 1:
        idx = int(index_parts[0])
        active_win = objreg.get("app").activeWindow()
        if active_win is None:
            # Not sure how you enter a command without an active window...
            raise cmdexc.CommandError(
                "No window specified and couldn't find active window!"
            )
        win_id = active_win.win_id

    if win_id not in objreg.window_registry:
        raise cmdexc.CommandError("There's no window with id {}!".format(win_id))

    tabbed_browser = objreg.get("tabbed-browser", scope="window", window=win_id)
    if not 0 < idx <= tabbed_browser.widget.count():
        raise cmdexc.CommandError("There's no tab with index {}!".format(idx))

    return (tabbed_browser, tabbed_browser.widget.widget(idx - 1))