clients/nested: fix boolean test

weston_check_egl_extension() returns a bool, not a pointer.

Fixes: ce5b614c80b4dfe8e899 "clients/nested: use weston_check_egl_extension
                             over strstr"
Cc: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Eric Engestrom <eric.engestrom@imgtec.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
diff --git a/clients/nested.c b/clients/nested.c
index 173076a..e9070e9 100644
--- a/clients/nested.c
+++ b/clients/nested.c
@@ -748,7 +748,7 @@
 
 	nested->egl_display = display_get_egl_display(nested->display);
 	extensions = eglQueryString(nested->egl_display, EGL_EXTENSIONS);
-	if (weston_check_egl_extension(extensions, "EGL_WL_bind_wayland_display") == NULL) {
+	if (!weston_check_egl_extension(extensions, "EGL_WL_bind_wayland_display")) {
 		fprintf(stderr, "no EGL_WL_bind_wayland_display extension\n");
 		return -1;
 	}