Fix HCheckValue::Canonicalize wrt uninitialized HConstant unique.

test/mjsunit/regress/regress-348280.js

Index: test/mjsunit/regress/regress-348280.js
diff --git a/test/mjsunit/regress/regress-347542.js b/test/mjsunit/regress/regress-348280.js
similarity index 55%
copy from test/mjsunit/regress/regress-347542.js
copy to test/mjsunit/regress/regress-348280.js
index 901d798fb7fbea45f0d9f3d8ba6c7a9846bf6dd6..319c270bef843c8b5202f3d699b8019ef9cdb1b5 100644
--- a/test/mjsunit/regress/regress-347542.js
+++ b/test/mjsunit/regress/regress-348280.js
@@ -4,8 +4,13 @@
 
 // Flags: --allow-natives-syntax
 
-function foo() {}
-foo();
-%OptimizeFunctionOnNextCall(foo);
-foo();
-%NeverOptimizeFunction(foo);
+function baz(f) { f(); }
+function goo() {}
+baz(goo);
+baz(goo);
+
+function bar(p) { if (p == 0) baz(1); }
+bar(1);
+bar(1);
+%OptimizeFunctionOnNextCall(bar);
+bar(1);