Fix JS compiler crash when translating external object fun with vararg

See KT-19793

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/BoxJsTestGenerated.java

@@ -6191,6 +6191,12 @@ public class BoxJsTestGenerated extends AbstractBoxJsTest {
             doTest(fileName);
         }
 
+        @TestMetadata("objectFunWithVararg.kt")
+        public void testObjectFunWithVararg() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("js/js.translator/testData/box/native/objectFunWithVararg.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("overrideNativeOverloadedFunction.kt")
         public void testOverrideNativeOverloadedFunction() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("js/js.translator/testData/box/native/overrideNativeOverloadedFunction.kt");

js/js.translator/src/org/jetbrains/kotlin/js/translate/reference/CallArgumentTranslator.kt

@@ -38,6 +38,7 @@ import org.jetbrains.kotlin.js.translate.utils.TranslationUtils
 import org.jetbrains.kotlin.js.translate.utils.getReferenceToJsClass
 import org.jetbrains.kotlin.psi.Call
 import org.jetbrains.kotlin.psi.ValueArgument
+import org.jetbrains.kotlin.resolve.DescriptorUtils
 import org.jetbrains.kotlin.resolve.calls.model.DefaultValueArgument
 import org.jetbrains.kotlin.resolve.calls.model.ResolvedCall
 import org.jetbrains.kotlin.resolve.calls.model.ResolvedValueArgument
@@ -150,6 +151,11 @@ class CallArgumentTranslator private constructor(
                 cachedReceiver = context().getOrDeclareTemporaryConstVariable(receiver)
                 result.add(0, cachedReceiver.reference())
             }
+            else if (DescriptorUtils.isObject(resolvedCall.resultingDescriptor.containingDeclaration)) {
+                cachedReceiver = context().getOrDeclareTemporaryConstVariable(
+                        ReferenceTranslator.translateAsValueReference(resolvedCall.resultingDescriptor.containingDeclaration, context()))
+                result.add(0, cachedReceiver.reference())
+            }
             else {
                 result.add(0, JsNullLiteral())
             }

js/js.translator/testData/box/native/objectFunWithVararg.js

@@ -0,0 +1,9 @@
+Test = {
+    test: function() {
+        var sum = 0;
+        for (var i = 0; i < arguments.length; ++i) {
+            sum += arguments[i];
+        }
+        return sum;
+    }
+};

js/js.translator/testData/box/native/objectFunWithVararg.kt

@@ -0,0 +1,13 @@
+// EXPECTED_REACHABLE_NODES: 995
+import Test.test
+
+external object Test {
+    fun test(vararg rest: Int): Int
+}
+
+fun box(): String {
+    val result = test(23, 42)
+    if (result != 65) return "fail: $result"
+
+    return "OK"
+}