Fix IfBuilder::Deopt to clear the current block.

test/mjsunit/regress/regress-crbug-243868.js

Index: test/mjsunit/regress/regress-crbug-243868.js
diff --git a/test/mjsunit/regress/regress-crbug-242870.js b/test/mjsunit/regress/regress-crbug-243868.js
similarity index 79%
copy from test/mjsunit/regress/regress-crbug-242870.js
copy to test/mjsunit/regress/regress-crbug-243868.js
index 7183375ca811cedc81c870d34e694e98cf727f9b..106d9cc78bce7795cd450fa0d07794f9f004a3af 100644
--- a/test/mjsunit/regress/regress-crbug-242870.js
+++ b/test/mjsunit/regress/regress-crbug-243868.js
@@ -29,15 +29,18 @@
 
 var non_const_true = true;
 
-function f() {
-  return (non_const_true || true && g());
+function f(o) {
+  return (non_const_true && (o.val == null || false));
 }
 
-function g() {
-  for (;;) {}
-}
+// Create an object with a constant function in another realm.
+var realm = Realm.create();
+var realmObject = Realm.eval(realm, "function g() {}; var o = { val:g }; o;")
+
+// Make the CompareNil IC in the function monomorphic.
+assertFalse(f(realmObject));
+assertFalse(f(realmObject));
 
-assertTrue(f());
-assertTrue(f());
+// Optimize the function containing the CompareNil IC.
 %OptimizeFunctionOnNextCall(f);
-assertTrue(f());
+assertFalse(f(realmObject));