idle-inhibit: fix use-after-free

A user reported a crash that only reproduces when preloading a hardened
malloc implementation. From the stack trace, this use-after-free seems
to be the most likely cause. Yay hardened malloc!

river/IdleInhibitor.zig

@@ -28,7 +28,8 @@ fn handleDestroy(listener: *wl.Listener(*wlr.IdleInhibitorV1), _: *wlr.IdleInhib
 
     const node = @fieldParentPtr(std.TailQueue(Self).Node, "data", self);
     server.idle_inhibitor_manager.inhibitors.remove(node);
-    util.gpa.destroy(node);
 
     self.inhibitor_manager.idleInhibitCheckActive();
+
+    util.gpa.destroy(node);
 }