https://newtab.firefoxchina.cn/newtab/as/activity-stream.html As shown in the picture, users should be able to change tabs freely on this page. But this caused some problems on my browser. These white tabs cannot be edited, moved or removed by me. My first two tabs are always blank (even if I try to change it and add a valid URL to it) and other tabs can be changed normally. When I tried to move a changed normal tab to the first one, I found that my changed tabs became blank and they could not be changed back to normal. This is very annoying for me. Please help me fix this problem