Fix appending text

This was broken in 6e954a1596.

doc/changelog.asciidoc

@@ -73,6 +73,7 @@ Fixed
 - Greasemonkey scripts which start with an UTF-8 BOM are now handled correctly.
 - When no documentation has been generated, the plaintext documentation now can
   be shown for more files such as `qute://help/userscripts.html`.
+- Crash when doing initial run on Wayland without XWayland
 
 Removed
 ~~~~~~~

qutebrowser/misc/backendproblem.py

@@ -247,9 +247,9 @@ def _handle_wayland():
                  "(if you have a <i>config.py</i> file, you'll need to set "
                  "this manually).</p>")
     else:
-        text.append("<p><b>Set up XWayland</b></p>"
-                    "<p>This allows you to use the newer QtWebEngine backend "
-                    "(based on Chromium). ")
+        text += ("<p><b>Set up XWayland</b></p>"
+                 "<p>This allows you to use the newer QtWebEngine backend "
+                 "(based on Chromium). ")
 
     if has_qt511:
         buttons.append(_Button("Force software rendering",