K2: fix exception in deserializer for external setter #KT-53031 Fixed

compiler/testData/codegen/box/fir/externalInDependency.kt

@@ -0,0 +1,18 @@
+// TARGET_BACKEND: JVM_IR
+
+// MODULE: m1
+// FILE: f1.kt
+
+object O {
+    var prop: String
+        external get
+        external set
+}
+
+// MODULE: m2(m1)
+// FILE: f2.kt
+
+fun box(): String {
+    O.hashCode() // Necessary to deserialize O
+    return "OK"
+}