KT-3214: Verify error when get array convention is used with varargs

#KT-3214 Can'tReproduce

compiler/testData/codegen/box/functions/kt3214.kt

@@ -0,0 +1,33 @@
+class A {
+    fun get(vararg x: Int) = x.size
+}
+
+class B {
+    fun get(vararg x: Unit) = x.size
+}
+
+fun test1(a: A): Int {
+    return a[1]
+}
+
+fun test2(a: A): Int {
+    return a[1, 2]
+}
+
+fun test3(b: B): Int {
+    return b[Unit.VALUE, Unit.VALUE]
+}
+
+
+fun box() : String {
+    var result = test1(A())
+    if (result != 1) return "fail1: $result"
+
+    result = test2(A())
+    if (result != 2) return "fail2: $result"
+
+    result = test3(B())
+    if (result != 2) return "fail3: $result"
+
+    return "OK"
+}