Fix [modify_side]switch_ai=data/dev/idle_ai.cfg

data/ai/dev/idle_ai.cfg

@@ -2,5 +2,9 @@
 [ai]
     id=idle_ai
     description=_"Multiplayer_AI^Dev AI: Idle AI" # wmllint: no spellcheck
-    #well, we can just fall back to idle ai. But we can just do nothing, and it will work (if no additional stages are brought in by other config sources - MP faction config, scenario config, era config, defaults, etc
+    # Needs to define at least one stage; otherwise, the default AI will be injected
+    # when used with [modify_side]switch_ai
+    [stage]
+    	name=empty
+    [/stage]
 [/ai]