# Buggy code
def tab_clone(self, bg=False, window=False):
    """Duplicate the current tab.

    Args:
        bg: Open in a background tab.
        window: Open in a new window.

    Return:
        The new QWebView.
    """
    cmdutils.check_exclusive((bg, window), "bw")
    curtab = self._current_widget()
    cur_title = self._tabbed_browser.page_title(self._current_index())
    try:
        history = curtab.history.serialize()
    except browsertab.WebTabError as e:
        raise cmdexc.CommandError(e)

    # The new tab could be in a new tabbed_browser (e.g. because of
    # tabs.tabs_are_windows being set)
    if window:
        new_tabbed_browser = self._new_tabbed_browser(
            private=self._tabbed_browser.private
        )
    else:
        new_tabbed_browser = self._tabbed_browser
    newtab = new_tabbed_browser.tabopen(background=bg)
    new_tabbed_browser = objreg.get(
        "tabbed-browser", scope="window", window=newtab.win_id
    )
    idx = new_tabbed_browser.indexOf(newtab)

    new_tabbed_browser.set_page_title(idx, cur_title)
    if config.val.tabs.favicons.show:
        new_tabbed_browser.setTabIcon(idx, curtab.icon())
        if config.val.tabs.tabs_are_windows:
            new_tabbed_browser.window().setWindowIcon(curtab.icon())

    newtab.data.keep_icon = True
    newtab.history.deserialize(history)
    newtab.zoom.set_factor(curtab.zoom.factor())
    new_tabbed_browser.set_tab_pinned(newtab, curtab.data.pinned)
    return newtab


# 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 tab_clone(self, bg=False, window=False):
    """Duplicate the current tab.

    Args:
        bg: Open in a background tab.
        window: Open in a new window.

    Return:
        The new QWebView.
    """
    cmdutils.check_exclusive((bg, window), "bw")
    curtab = self._current_widget()
    cur_title = self._tabbed_browser.widget.page_title(self._current_index())
    try:
        history = curtab.history.serialize()
    except browsertab.WebTabError as e:
        raise cmdexc.CommandError(e)

    # The new tab could be in a new tabbed_browser (e.g. because of
    # tabs.tabs_are_windows being set)
    if window:
        new_tabbed_browser = self._new_tabbed_browser(
            private=self._tabbed_browser.private
        )
    else:
        new_tabbed_browser = self._tabbed_browser
    newtab = new_tabbed_browser.tabopen(background=bg)
    new_tabbed_browser = objreg.get(
        "tabbed-browser", scope="window", window=newtab.win_id
    )
    idx = new_tabbed_browser.widget.indexOf(newtab)

    new_tabbed_browser.widget.set_page_title(idx, cur_title)
    if curtab.data.should_show_icon():
        new_tabbed_browser.widget.setTabIcon(idx, curtab.icon())
        if config.val.tabs.tabs_are_windows:
            new_tabbed_browser.widget.window().setWindowIcon(curtab.icon())

    newtab.data.keep_icon = True
    newtab.history.deserialize(history)
    newtab.zoom.set_factor(curtab.zoom.factor())
    new_tabbed_browser.widget.set_tab_pinned(newtab, curtab.data.pinned)
    return newtab