AbstractSingletonService: use more specific type

The LazyObjects instance will definitely return a collection of objects
of type PT, not just Object. This distinction is important now that the
ObjectIndex is more selective about which pending objects it resolves.

Author: ctrueden

src/main/java/org/scijava/plugin/AbstractSingletonService.java

@@ -80,11 +80,11 @@ public <P extends PT> P getInstance(final Class<P> pluginClass) {
 	@Override
 	public void initialize() {
 		// add singleton instances to the object index... IN THE FUTURE!
-		objectService.getIndex().addLater(new LazyObjects<Object>() {
+		objectService.getIndex().addLater(new LazyObjects<PT>() {
 
 			@Override
-			public ArrayList<Object> get() {
-				return new ArrayList<Object>(getInstances());
+			public ArrayList<PT> get() {
+				return new ArrayList<PT>(getInstances());
 			}
 		});
 	}