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)
         }
     }