Description of problem:
I was scrolling through my list of feed items using ctrl+j, that's it.

Version-Release number of selected component:
gnome-feeds-0.13.4-4.fc32

Additional info:
reporter:       libreport-2.13.1
cgroup:         0::/user.slice/user-1000.slice/user/gnome-launched-org.gabmus.gfeeds.desktop-298233.scope
cmdline:        /usr/bin/python3 /usr/bin/gfeeds
crash_function: guess_decode
exception_type: AttributeError
executable:     /usr/bin/gfeeds
interpreter:    python3-3.8.3-1.fc32.x86_64
kernel:         5.6.16-300.fc32.x86_64
runlevel:       N 5
type:           Python3
uid:            1000

Truncated backtrace:
util.py:310:guess_decode:AttributeError: 'NoneType' object has no attribute 'decode'

Traceback (most recent call last):
  File "/usr/lib/python3.8/site-packages/gfeeds/app_window.py", line 244, in on_sidebar_row_activated
    self.webview.load_feeditem(row.feeditem)
  File "/usr/lib/python3.8/site-packages/gfeeds/webview.py", line 193, in load_feeditem
    self.set_enable_rss_content(True, feeditem)
  File "/usr/lib/python3.8/site-packages/gfeeds/webview.py", line 128, in set_enable_rss_content
    self._load_rss_content(self.feeditem)
  File "/usr/lib/python3.8/site-packages/gfeeds/webview.py", line 159, in _load_rss_content
    self.set_enable_reader_mode(True, True)
  File "/usr/lib/python3.8/site-packages/gfeeds/webview.py", line 264, in set_enable_reader_mode
    self._set_enable_reader_mode_async_callback()
  File "/usr/lib/python3.8/site-packages/gfeeds/webview.py", line 237, in _set_enable_reader_mode_async_callback
    self.webkitview.load_html(build_reader_html(
  File "/usr/lib/python3.8/site-packages/gfeeds/build_reader_html.py", line 110, in build_reader_html
    syntax_highlight_css, root = build_syntax_highlight_from_raw_html(content)
  File "/usr/lib/python3.8/site-packages/gfeeds/build_reader_html.py", line 78, in build_syntax_highlight_from_raw_html
    return build_syntax_highlight(
  File "/usr/lib/python3.8/site-packages/gfeeds/build_reader_html.py", line 59, in build_syntax_highlight
    lexer = pygments.lexers.guess_lexer(code_node.text)
  File "/usr/lib/python3.8/site-packages/pygments/lexers/__init__.py", line 297, in guess_lexer
    _text, _ = guess_decode(_text)
  File "/usr/lib/python3.8/site-packages/pygments/util.py", line 310, in guess_decode
    text = text.decode('utf-8')
AttributeError: 'NoneType' object has no attribute 'decode'

Local variables in innermost frame:
text: None