Don't crash on tear-down of Workspace if run without X11 support

Much easier than expected.

netinfo.cpp

@@ -129,7 +129,9 @@ RootInfo *RootInfo::create()
 
 void RootInfo::destroy()
 {
-    Q_ASSERT(s_self);
+    if (!s_self) {
+        return;
+    }
     xcb_window_t supportWindow = s_self->supportWindow();
     delete s_self;
     s_self = NULL;

workspace.cpp

@@ -512,7 +512,10 @@ Workspace::~Workspace()
     Client::cleanupX11();
     for (UnmanagedList::iterator it = unmanaged.begin(), end = unmanaged.end(); it != end; ++it)
         (*it)->release(ReleaseReason::KWinShutsDown);
-    xcb_delete_property(connection(), rootWindow(), atoms->kwin_running);
+
+    if (auto c = kwinApp()->x11Connection()) {
+        xcb_delete_property(c, kwinApp()->x11RootWindow(), atoms->kwin_running);
+    }
 
     for (auto it = deleted.begin(); it != deleted.end();) {
         emit deletedRemoved(*it);