[gnome-games] platform-register: Mark get_platform() return result as nullable

[Alexander Mikhaylenko <alexm src gnome org>]

commit d55bd93536ac300bd48ab65510ce56cf237be5d4
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Wed Feb 19 15:45:39 2020 +0500

    platform-register: Mark get_platform() return result as nullable

 src/core/platform-register.vala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/core/platform-register.vala b/src/core/platform-register.vala
index b03290dc..c3021109 100644
--- a/src/core/platform-register.vala
+++ b/src/core/platform-register.vala
@@ -35,7 +35,7 @@ private class Games.PlatformRegister : Object {
                return result;
        }
 
-       public Platform get_platform (string id) {
+       public Platform? get_platform (string id) {
                return platforms[id];
        }
 }