[Wasm] Fix access to WebIDL dictionary members

Evaluate external interface companion objects as an empty JS object
instead of null due to null checks on interop boundary.

^KT-59082 Fixed

compiler/testData/codegen/boxWasmJsInterop/kt59082.kt

@@ -0,0 +1,15 @@
+// TARGET_BACKEND: WASM
+
+@JsName("null")
+@Suppress("NESTED_CLASS_IN_EXTERNAL_INTERFACE")
+public external interface CanvasFillRule : JsAny {
+    companion object
+}
+
+public inline val CanvasFillRule.Companion.EVENODD: CanvasFillRule get() =
+    "evenodd".toJsString().unsafeCast<CanvasFillRule>()
+
+fun box(): String {
+    if (CanvasFillRule.EVENODD.toString() != "evenodd") return "Fail 1"
+    return "OK"
+}