Making var arg kParameters default to empty array no argument given

fixes KT-29969

compiler/testData/codegen/box/reflection/callBy/emptyVarArg.kt

@@ -0,0 +1,19 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+// IGNORE_BACKEND: JS_IR
+// IGNORE_BACKEND: JS, NATIVE
+
+// WITH_REFLECT
+
+import kotlin.test.assertEquals
+
+fun join(vararg strings: String) = strings.toList().joinToString("")
+
+fun sum(vararg bytes: Byte) = bytes.toList().fold(0) { acc, el -> acc + el }
+
+fun box(): String {
+    val j = ::join
+    val s = ::sum
+    assertEquals("", j.callBy(emptyMap()))
+    assertEquals(0, s.callBy(emptyMap()))
+    return "OK"
+}

compiler/testData/codegen/box/reflection/createAnnotation/callByWithEmptyVarArg.kt

@@ -0,0 +1,25 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+// IGNORE_BACKEND: JS_IR
+// IGNORE_BACKEND: JS, NATIVE
+
+// WITH_REFLECT
+
+import kotlin.reflect.*
+import kotlin.reflect.full.*
+import kotlin.test.assert
+
+annotation class Foo(vararg val strings: String)
+
+annotation class Bar(vararg val bytes: Byte)
+
+fun box(): String {
+    val fooConstructor = Foo::class.primaryConstructor!!
+    val foo = fooConstructor.callBy(emptyMap())
+    assert(foo.strings.isEmpty())
+
+    val barConstructor = Bar::class.primaryConstructor!!
+    val bar = barConstructor.callBy(emptyMap())
+    assert(bar.bytes.isEmpty())
+
+    return "OK"
+}