Fix IrFunction.isEmptyArray implementation

The previous one was incorrect for K1 since parent of top-level function
is `IrClass`, not `IrPackageFragment`.

The change is non-functional, K1 still worked correctly, but had to do
some extra work when inlining `emptyArray` calls and produces less
performant bytecode.

compiler/testData/codegen/box/arrays/emptyArrayDesugaring.kt

@@ -0,0 +1,12 @@
+// WITH_STDLIB
+// TARGET_BACKEND: JVM_IR
+
+// Checks if emptyArray call has been lowered
+
+fun box(): String {
+    emptyArray<String>()
+    return "OK"
+}
+
+// CHECK_BYTECODE_TEXT
+// 0 ISTORE 0