Fixed edge case response

src/endpoints/bettwaage.py

@@ -73,6 +73,8 @@ async def add_weight(tl: int, tr: int, bl: int, br: int):
 
 @router.post("/latest")
 async def get_latest():
+    if not latest_values:
+        return HTMLResponse(status_code=200, content="No data given yet")
     total = sum(latest_values)
     return JSONResponse(
         {