[KxSerialization] Fix NPE when accessing delegated property

Kotlin 1.7.20 added optimizations for delegated properties on the JVM,
which broke serialization for optimized properties. Commit bfeff81
tried to fix that, but broke non-optimized delegated properties. This
commit restores correct serialization for optimized and non-optimized
properties, also ensuring that it only affects the JVM target.

 #KT-58954 Fixed
 #KT-59113 Fixed

plugins/kotlinx-serialization/kotlinx-serialization.backend/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/SerializableIrGenerator.kt

@@ -6,6 +6,7 @@
 package org.jetbrains.kotlinx.serialization.compiler.backend.ir
 
 import org.jetbrains.kotlin.backend.common.lower.irThrow
+import org.jetbrains.kotlin.backend.jvm.lower.isJvmOptimizableDelegate
 import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.descriptors.DescriptorVisibilities
 import org.jetbrains.kotlin.descriptors.ValueParameterDescriptor
@@ -21,6 +22,7 @@ import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.platform.jvm.isJvm
 import org.jetbrains.kotlin.util.OperatorNameConventions
 import org.jetbrains.kotlin.utils.getOrPutNullable
 import org.jetbrains.kotlinx.serialization.compiler.extensions.SerializationPluginContext
@@ -82,8 +84,10 @@ class SerializableIrGenerator(
                     it is IrProperty && it.backingField != null -> {
                         if (it in serialDescs) {
                             current = it
-                        } else if (it.backingField?.initializer != null && !it.isDelegated) {
-                            // skip transient lateinit or deferred properties (with null initializer)
+                        } else if (it.backingField?.initializer != null &&
+                            !(it.isJvmOptimizableDelegate() && compilerContext.platform.isJvm())
+                        ) {
+                            // skip transient lateinit or deferred properties (with null initializer) and optimized delegations
                             val expression = initializerAdapter(it.backingField!!.initializer!!)
 
                             statementsAfterSerializableProperty.getOrPutNullable(current, { mutableListOf() })