try to get a bit more coverage

Author: SylvainJuge

sdk-extensions/incubator/src/test/java/io/opentelemetry/sdk/extension/incubator/fileconfig/ResourceFactoryTest.java

@@ -142,10 +142,14 @@ private static Stream<Arguments> createWithDetectorsArgs() {
             Collections.singletonList("*o*"),
             Collections.singletonList("order"),
             Resource.getDefault().toBuilder().put("color", "red").build()),
-        // empty include should be treated as include all
+        // empty or missing include should be treated as include all
         Arguments.of(
             Collections.emptyList(),
             Collections.singletonList("order"),
+            Resource.getDefault().toBuilder().put("color", "red").put("shape", "square").build()),
+        Arguments.of(
+            null,
+            Collections.singletonList("order"),
             Resource.getDefault().toBuilder().put("color", "red").put("shape", "square").build()));
   }