Generate multi-files facade even if it's empty

It still contains useful information about it's parts,
that may be used while building stubs for multi-file group
containing only InlineOnly functions

compiler/backend/src/org/jetbrains/kotlin/codegen/MultifileClassCodegen.kt

@@ -113,7 +113,7 @@ class MultifileClassCodegen(
 
         generateDelegatesToPreviouslyCompiledParts(generateCallableMemberTasks, partFqNames)
 
-        if (!generateCallableMemberTasks.isEmpty()) {
+        if (!partFqNames.isEmpty()) {
             generateMultifileFacadeClass(generateCallableMemberTasks, partFqNames)
         }
     }

compiler/testData/codegen/bytecodeListing/emptyMultifileFacade.kt

@@ -0,0 +1,5 @@
+@file:[JvmName("Foo") JvmMultifileClass]
+package test
+
+// This test checks that we generate empty multi-file facade even if there is no delegates within it (only private functions in packages)
+private fun privateOnly() {}

compiler/testData/codegen/bytecodeListing/emptyMultifileFacade.txt

@@ -0,0 +1,9 @@
+@kotlin.Metadata
+@kotlin.jvm.internal.KotlinMultifileClass
+public final class test/Foo
+
+@kotlin.Metadata
+@kotlin.jvm.internal.KotlinMultifileClassPart
+synthetic final class test/Foo__EmptyMultifileFacadeKt {
+    private final static method privateOnly(): void
+}

compiler/tests/org/jetbrains/kotlin/codegen/BytecodeListingTestGenerated.java

@@ -41,6 +41,12 @@ public class BytecodeListingTestGenerated extends AbstractBytecodeListingTest {
         doTest(fileName);
     }
 
+    @TestMetadata("emptyMultifileFacade.kt")
+    public void testEmptyMultifileFacade() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeListing/emptyMultifileFacade.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("inlineOnly.kt")
     public void testInlineOnly() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeListing/inlineOnly.kt");