macos: restore 0 blur-radius when reloading config (#3954)

If a blur radius config value was previously set but then removed or set
to 0, the new blur radius would not take effect on config reload due to
the early return clause.

src/apprt/embedded.zig

@@ -1891,9 +1891,6 @@ pub const CAPI = struct {
         // Do nothing if we don't have background transparency enabled
         if (config.@"background-opacity" >= 1.0) return;
 
-        // Do nothing if our blur value is zero
-        if (config.@"background-blur-radius" == 0) return;
-
         const nswindow = objc.Object.fromId(window);
         _ = CGSSetWindowBackgroundBlurRadius(
             CGSDefaultConnectionForThread(),