Fixes a minor recurring runtime in origin selection (#4679)

# About the pull request

Harry forgot to account for indecisive people

No user changes, just gets rid of a recurring runtime in live game logs

code/modules/client/preferences.dm

@@ -1701,6 +1701,8 @@ var/const/MAX_SAVE_SLOTS = 10
 				if("origin")
 					var/choice = tgui_input_list(user, "Please choose your character's origin.", "Origin Selection", GLOB.player_origins)
 					var/datum/origin/picked_choice = GLOB.origins[choice]
+					if(!picked_choice)
+						return
 					if(tgui_alert(user, "You've selected [picked_choice.name]. [picked_choice.desc]", "Selected Origin", list("Confirm", "Cancel")) == "Cancel")
 						return
 					if(choice)