Fix compile error

Author: calmilamsy

src/main/java/io/github/prospector/modmenu/util/TestModContainer.java

@@ -90,6 +90,11 @@ public String getId() {
 			return this.id;
 		}
 
+		@Override
+		public Collection<String> getProvides() {
+			return null;
+		}
+
 		@Override
 		public Version getVersion() {
 			return this.version;