Fix #9562: Handle case of invalid action2 with zero results. (#9564)

(cherry picked from commit 7e70ead396)

src/newgrf.cpp

@@ -5378,6 +5378,11 @@ static void NewSpriteGroup(ByteReader *buf)
 						return;
 					}
 
+					if (num_loaded + num_loading == 0) {
+						grfmsg(1, "NewSpriteGroup: no result, skipping invalid RealSpriteGroup");
+						break;
+					}
+
 					assert(RealSpriteGroup::CanAllocateItem());
 					RealSpriteGroup *group = new RealSpriteGroup();
 					group->nfo_line = _cur.nfo_line;