Revert of Add null check to animations for registered custom property initial values

third_party/WebKit/LayoutTests/animations/custom-properties/empty-initial-value-crash.html

-<script src="../../resources/testharness.js"></script>
-<script src="../../resources/testharnessreport.js"></script>
-<style>
-#target {
-  --x: initial;
-}
-</style>
-<div id="target"></div>
-<script>
-setup(() => {
-  CSS.registerProperty({name: '--x'});
-});
-
-test(() => {
-  var animation = target.animate({'--x': 'test'}, 1);
-  assert_equals(getComputedStyle(target).getPropertyValue('--x'), '');
-  animation.cancel();
-}, 'Do not crash when animating with an underlying value of initial');
-
-test(() => {
-  var animation = target.animate({'--x': 'initial'}, {fill: 'forwards'});
-  assert_equals(getComputedStyle(target).getPropertyValue('--x'), '');
-  animation.cancel();
-}, 'Do not crash when animating an empty initial value');
-
-test(() => {
-  var animation = target.animate({'--x': 'inherit'}, {fill: 'forwards'});
-  assert_equals(getComputedStyle(target).getPropertyValue('--x'), '');
-  animation.cancel();
-}, 'Do not crash when animating an inherited empty initial value');
-</script>