[K/N][IR][caches] Fixed problems with inline classes

Fixes https://youtrack.jetbrains.com/issue/KT-50978

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/lazy/IrLazyClass.kt

@@ -75,6 +75,7 @@ class IrLazyClass(
     private fun shouldBuildStub(descriptor: DeclarationDescriptor): Boolean =
         descriptor !is DeclarationDescriptorWithVisibility ||
                 !DescriptorVisibilities.isPrivate(descriptor.visibility) ||
+                // This exception is needed for K/N caches usage.
                 isObject && descriptor is ClassConstructorDescriptor
 
     override var typeParameters: List<IrTypeParameter> by lazyVar(stubGenerator.lock) {

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/InlineClasses.kt

@@ -5,6 +5,7 @@
 
 package org.jetbrains.kotlin.backend.konan
 
+import org.jetbrains.kotlin.backend.common.atMostOne
 import org.jetbrains.kotlin.backend.common.ir.isTopLevel
 import org.jetbrains.kotlin.backend.konan.descriptors.findPackage
 import org.jetbrains.kotlin.backend.konan.ir.getSuperClassNotAny
@@ -305,7 +306,8 @@ internal object IrTypeInlineClassesSupport : InlineClassesSupport<IrClass, IrTyp
 
     override fun getInlinedClassUnderlyingType(clazz: IrClass): IrType =
             clazz.constructors.firstOrNull { it.isPrimary }?.valueParameters?.single()?.type
-                    ?: clazz.declarations.filterIsInstance<IrProperty>().single { it.backingField != null }.backingField!!.type
+                    ?: clazz.declarations.filterIsInstance<IrProperty>().atMostOne { it.backingField != null }?.backingField?.type
+                    ?: clazz.inlineClassRepresentation!!.underlyingType
 
     override fun getPackageFqName(clazz: IrClass) =
             clazz.packageFqName