Allow empty single-line bodies in property accessors

idea/testData/codeInsight/overrideImplement/overrideMutableExtensionProperty.kt.after

@@ -5,6 +5,5 @@ interface A {
 class B : A {
     override var Int.foo: Double
         get() = <selection><caret>TODO("not implemented")</selection> //To change initializer of created properties use File | Settings | File Templates.
-        set(value) {
-        }
+        set(value) {}
 }