Add xcb error assertions instead of segfaulting

These things should not fail (and I've never seen one of these thing
error out with yabridge), but in the case they do an assertion is at
least a lot trace down than a segfault.

src/wine-host/editor.cpp

@@ -221,6 +221,8 @@ void Editor::handle_x11_events() const {
 }
 
 void Editor::fix_local_coordinates() const {
+    xcb_generic_error_t* error;
+
     // We're purposely not using XEmbed. This has the consequence that wine
     // still thinks that any X and Y coordinates are relative to the x11 window
     // root instead of the parent window provided by the DAW, causing all sorts
@@ -235,7 +237,8 @@ void Editor::fix_local_coordinates() const {
     const auto query_cookie =
         xcb_query_tree(x11_connection.get(), parent_window);
     xcb_window_t root =
-        xcb_query_tree_reply(x11_connection.get(), query_cookie, nullptr)->root;
+        xcb_query_tree_reply(x11_connection.get(), query_cookie, &error)->root;
+    assert(!error);
 
     // We can't directly use the `event.x` and `event.y` coordinates because the
     // parent window may also be embedded inside another window.
@@ -243,7 +246,8 @@ void Editor::fix_local_coordinates() const {
         x11_connection.get(), parent_window, root, 0, 0);
     const xcb_translate_coordinates_reply_t* translated_coordinates =
         xcb_translate_coordinates_reply(x11_connection.get(), translate_cookie,
-                                        nullptr);
+                                        &error);
+    assert(!error);
 
     xcb_configure_notify_event_t translated_event{};
     translated_event.response_type = XCB_CONFIGURE_NOTIFY;
@@ -348,19 +352,24 @@ LRESULT CALLBACK window_proc(HWND handle,
 
 xcb_window_t find_topmost_window(xcb_connection_t& x11_connection,
                                  xcb_window_t starting_at) {
+    xcb_generic_error_t* error;
+
     xcb_window_t current_window = starting_at;
 
     xcb_query_tree_cookie_t query_cookie =
         xcb_query_tree(&x11_connection, starting_at);
     xcb_query_tree_reply_t* query_reply =
-        xcb_query_tree_reply(&x11_connection, query_cookie, nullptr);
+        xcb_query_tree_reply(&x11_connection, query_cookie, &error);
+    assert(!error);
+
     xcb_window_t root = query_reply->root;
     while (query_reply->parent != root) {
         current_window = query_reply->parent;
 
         query_cookie = xcb_query_tree(&x11_connection, current_window);
         query_reply =
-            xcb_query_tree_reply(&x11_connection, query_cookie, nullptr);
+            xcb_query_tree_reply(&x11_connection, query_cookie, &error);
+        assert(!error);
     }
 
     return current_window;