fix(xlib): handle None return from get_wm_name() on KDE Plasma (#115)

When no WM_NAME property exists on a window (common on KDE Plasma with
Fedora), window.get_wm_name() returns None. The isinstance(r, str)
check doesn't catch None, so it falls through to r.decode("latin1")
which raises AttributeError: 'NoneType' object has no attribute 'decode'.

Add a None guard that returns "unknown", matching the existing error
handling pattern in the function.

Fixes #114

Author: TimeToBuildBob

aw_watcher_window/xlib.py

@@ -76,7 +76,9 @@ def get_window_name(window: Window) -> str:
         try:
             # Fallback.
             r = window.get_wm_name()
-            if isinstance(r, str):
+            if r is None:
+                return "unknown"
+            elif isinstance(r, str):
                 return r
             else:
                 logger.warning(