Test Engine: fixed mismatched macro signature when disabled.

The macro was actually unused in our code if IMGUI_ENABLE_TEST_ENGINE is not defined, but can affect third-party code.

imgui_internal.h

@@ -3921,7 +3921,7 @@ extern const char*  ImGuiTestEngine_FindItemDebugLabel(ImGuiContext* ctx, ImGuiI
 #define IMGUI_TEST_ENGINE_ITEM_INFO(_ID,_LABEL,_FLAGS)      if (g.TestEngineHookItems) ImGuiTestEngineHook_ItemInfo(&g, _ID, _LABEL, _FLAGS)    // Register item label and status flags (optional)
 #define IMGUI_TEST_ENGINE_LOG(_FMT,...)                     ImGuiTestEngineHook_Log(&g, _FMT, __VA_ARGS__)                                      // Custom log entry from user land into test log
 #else
-#define IMGUI_TEST_ENGINE_ITEM_ADD(_BB,_ID)                 ((void)0)
+#define IMGUI_TEST_ENGINE_ITEM_ADD(_ID,_BB,_ITEM_DATA)      ((void)0)
 #define IMGUI_TEST_ENGINE_ITEM_INFO(_ID,_LABEL,_FLAGS)      ((void)g)
 #endif