Fix KAnnotatedElement.findAnnotation when no annotation is found

#KT-15540 Fixed

compiler/testData/codegen/box/reflection/annotations/findAnnotation.kt

@@ -2,6 +2,7 @@
 // WITH_REFLECT
 
 import kotlin.reflect.findAnnotation
+import kotlin.test.assertNull
 
 annotation class Yes(val value: String)
 annotation class No(val value: String)
@@ -10,6 +11,11 @@ annotation class No(val value: String)
 @No("Fail")
 class Foo
 
+class Bar
+
 fun box(): String {
+    assertNull(Bar::class.findAnnotation<Yes>())
+    assertNull(Bar::class.findAnnotation<No>())
+
     return Foo::class.findAnnotation<Yes>()?.value ?: "Fail: no annotation"
 }