@extend; causes an unexpected exception

[xorraxraxret]

Reproduction:

.a {
    @extend;
}

Log:

Unexpected exception:
TypeError: null: type 'JSNull' is not a subtype of type 'Expression'

node_modules/sass/sass.dart.js 2286:43   Object.wrapException
node_modules/sass/sass.dart.js 3798:15   Object._failedAsCheck
node_modules/sass/sass.dart.js 3787:9    Rti._generalAsCheckImplementation
node_modules/sass/sass.dart.js 3734:22   Rti._installSpecializedAsCheck
node_modules/sass/sass.dart.js 56647:31  InterpolationMap._mapLocation$1
node_modules/sass/sass.dart.js 56551:22  InterpolationMap.mapSpan$1
node_modules/sass/sass.dart.js 56535:24  InterpolationMap.mapException$1
node_modules/sass/sass.dart.js 58600:34  SelectorParser.wrapSpanFormatException$1$1
node_modules/sass/sass.dart.js 58642:19  SelectorParser.wrapSpanFormatException$1
node_modules/sass/sass.dart.js 59439:19  SelectorParser.parse$0

Expected:
An error response similar to the one that occurs when doing the same with other functions, eg. @use;