JVM IR: Don't produce CHECKCASTs on null constants (KT-36650)

compiler/testData/codegen/box/classes/kt1018.kt

@@ -1,3 +1,6 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+// The IR prduced by FIR implicitly casts `null` of type `Nothing?` to type `Int` instead of `Int?` in `getColumnCount`.
+
 public class StockMarketTableModel() {
 
     public fun getColumnCount() : Int {

compiler/testData/codegen/box/coroutines/tailCallOptimizations/crossinline_ir.txt

@@ -2,7 +2,6 @@
 @kotlin.coroutines.jvm.internal.DebugMetadata
 public final class CrossinlineKt$box$1$invokeSuspend$$inlined$filter$1$1 {
     field L$0: java.lang.Object
-    field L$1: java.lang.Object
     field label: int
     synthetic field result: java.lang.Object
     synthetic final field this$0: CrossinlineKt$box$1$invokeSuspend$$inlined$filter$1
@@ -98,7 +97,6 @@ public final class CrossinlineKt$consumeEach$2 {
 @kotlin.coroutines.jvm.internal.DebugMetadata
 public final class CrossinlineKt$filter$$inlined$source$1$1 {
     field L$0: java.lang.Object
-    field L$1: java.lang.Object
     field label: int
     synthetic field result: java.lang.Object
     synthetic final field this$0: CrossinlineKt$filter$$inlined$source$1
@@ -190,7 +188,6 @@ public final class CrossinlineKt$range$$inlined$source$1$1 {
     field I$1: int
     field L$0: java.lang.Object
     field L$1: java.lang.Object
-    field L$2: java.lang.Object
     field label: int
     synthetic field result: java.lang.Object
     synthetic final field this$0: CrossinlineKt$range$$inlined$source$1
@@ -216,7 +213,6 @@ public final class CrossinlineKt$range$$inlined$source$1 {
 public final class CrossinlineKt$source$1$consume$1 {
     // source: 'crossinline.kt'
     field L$0: java.lang.Object
-    field L$1: java.lang.Object
     field label: int
     synthetic field result: java.lang.Object
     synthetic final field this$0: CrossinlineKt$source$1