Fix for KT-5995: Labeled val causes an exception from the back-end

#KT-5995 Fixed

compiler/testData/codegen/box/labels/labeledDeclarations.kt

@@ -0,0 +1,16 @@
+data class A(val a: Int, val b: Int)
+
+fun box() : String
+{
+    @a val x = 1
+    @b fun a() = 2
+    @c val (z, z2) = A(1, 2)
+
+    if (x != 1) return "fail 1"
+
+    if (a() != 2) return "fail 2"
+
+    if (z != 1 || z2 != 2) return "fail 3"
+
+    return "OK"
+}

compiler/testData/codegen/box/labels/labeledDeclarations2.kt

@@ -0,0 +1,16 @@
+data class A(val a: Int, val b: Int)
+
+fun box() : String
+{
+    (@a val x = 1)
+    (@b fun a() = 2)
+    (@c val (z, z2) = A(1, 2))
+
+    if (x != 1) return "fail 1"
+
+    if (a() != 2) return "fail 2"
+
+    if (z != 1 || z2 != 2) return "fail 3"
+
+    return "OK"
+}