Cursor: use inflight_mode as needed in updateState()

This fixes possible assertion failures when quickly cancelling and
starting a new move/resize. The following steps, take from the bug
report, can currently reproduce the race:

1. Start with a window in tiled mode.
2. Begin resizing the window with your cursor.
3. Send the window back to tiled mode (with a keybind) and quickly begin
resizing it again with your cursor.

river/Cursor.zig

@@ -996,6 +996,23 @@ pub fn updateState(self: *Self) void {
         },
         // TODO: Leave down mode if the target surface is no longer visible.
         .down => assert(!self.hidden),
+        .move, .resize => {
+            // Moving and resizing of views is handled through the transaction system. Therefore,
+            // we must inspect the inflight_mode instead if a move or a resize is in progress.
+            //
+            // The cases when a move/resize is being started or ended and e.g. mode is resize
+            // while inflight_mode is passthrough or mode is passthrough while inflight_mode
+            // is resize shouldn't need any special handling.
+            //
+            // In the first case, a move/resize has been started along with a transaction but the
+            // transaction hasn't been committed yet so there is nothing to do.
+            //
+            // In the second case, a move/resize has been terminated by the user but the
+            // transaction carrying out the final size/position change is still inflight.
+            // Therefore, the user already expects the cursor to be free from the view and
+            // we should not warp it back to the fixed offset of the move/resize.
+            switch (self.inflight_mode) {
+                .passthrough, .down => {},
                 inline .move, .resize => |data, mode| {
                     assert(!self.hidden);
 
@@ -1028,6 +1045,8 @@ pub fn updateState(self: *Self) void {
                     self.wlr_cursor.warpClosest(null, new_x, new_y);
                 },
             }
+        },
+    }
 }
 
 /// Pass an event on to the surface under the cursor, if any.