Fix new warnings in project code

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/MutableController.kt

@@ -35,6 +35,7 @@ open class MutableController(val context: JsIrBackendContext, val lowerings: Lis
                                     }
                                 }
                             }
+                            is ModuleLowering -> {}
                         }
                     }
                     declaration.loweredUpTo = i

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/export/ExportModelGenerator.kt

@@ -151,6 +151,7 @@ class ExportModelGenerator(val context: JsIrBackendContext) {
         when (val exportability = classExportability(klass)) {
             is Exportability.Prohibited -> error(exportability.reason)
             is Exportability.NotNeeded -> return null
+            Exportability.Allowed -> {}
         }
 
         val members = mutableListOf<ExportedDeclaration>()