Kotlin: Exclude .kt files from non serializable field query

java/ql/src/Likely Bugs/Serialization/NonSerializableField.ql

@@ -90,7 +90,7 @@ predicate exceptions(Class c, Field f) {
 
 from Class c, Field f, string reason
 where
-  c.fromSource() and
+  c.getFile().isJavaSourceFile() and
   c.getAStrictAncestor() instanceof TypeSerializable and
   f.getDeclaringType() = c and
   not exceptions(c, f) and

java/ql/test/kotlin/query-tests/NonSerializableField/NonSerializableField.expected

@@ -1 +0,0 @@
-| NonSerializableFieldTest.kt:3:22:3:28 | <dispatchReceiver> | This field is in a serializable class, but is not serializable itself because Foo is not serializable. |