Bug fix for WaitClient, WaitGL and WaitNative It is valid to call eglWaitClient, eglWaitGL and eglWaitNative when there is no active context in the current thread. Update code to account for that possibility. Bug: angleproject:5898 Test: EGLSyncTest.WaitClient* EGLSyncTest.WaitGL* EGLSyncTest.WaitNative* Change-Id: I81f05a27f1f641cf8986e2e6c05c183ea8471889 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2849587 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Mohan Maiya <m.maiya@samsung.com>