ozone/wayland: |data_device_| might be null

Fix crash that happens in tests if there is no data_device_.

PS: we don't have tests running in our bot yet. This is what I
observer, when did first runs locally.

Bug: 578890
Change-Id: I6b9b01fb1f29b71f6fb459b9c69d4967cbb99b95
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2062441
Commit-Queue: Maksim Sisov <msisov@igalia.com>
Reviewed-by: Antonio Gomes <tonikitoo@igalia.com>
Cr-Commit-Position: refs/heads/master@{#743003}
diff --git a/ui/ozone/platform/wayland/host/wayland_connection.cc b/ui/ozone/platform/wayland/host/wayland_connection.cc
index aab87380..f48eafb 100644
--- a/ui/ozone/platform/wayland/host/wayland_connection.cc
+++ b/ui/ozone/platform/wayland/host/wayland_connection.cc
@@ -174,6 +174,9 @@
 }
 
 bool WaylandConnection::IsDragInProgress() {
+  // |data_device_| can be null when running on headless weston.
+  if (!data_device_)
+    return false;
   return data_device_->IsDragEntered() || drag_data_source();
 }