[JS IR] Fix unsgined integer default arguemtns (KT-44180)

Const lowering didn't exprect null constants with unsigned number
types and crashed with NPE. This commit fixes that.

compiler/testData/codegen/box/unsignedTypes/defaultArguments.kt

@@ -0,0 +1,20 @@
+// WITH_RUNTIME
+
+// Case of KT-44180
+
+fun foo(
+    p0: UByte = 1u,
+    p1: UShort = 1u,
+    p2: UInt = 1u,
+    p4: ULong = 1uL,
+): ULong {
+    return p0.toULong() + p1.toUShort() + p2.toUInt() + p4
+}
+
+fun box(): String {
+    if (foo() != 4uL) return "Fail 1"
+    if (foo(p2 = 10u) != 13uL) return "Fail 2"
+    if (foo(10u, 10u, 10u, 10uL) != 40uL) return "Fail 3"
+
+    return "OK"
+}