invalid json response body at https://api.isavukatim.com/kategorifilter/?kategori=genelsagliksigortasi reason: Unexpected token O in JSON at position 0

FetchError: invalid json response body at https://api.isavukatim.com/kategorifilter/?kategori=genelsagliksigortasi reason: Unexpected token O in JSON at position 0
    at /home/isavukatimnextuser/isavukatim/node_modules/node-fetch/lib/index.js:241:32
    at process._tickCallback (internal/process/next_tick.js:68:7)