Cant close masteries in champ select

in a ranked game today (literally a minute ago) i was first pick on my team and finished the bans my friend was asking me a question about a specific mastery and when i opened up the mastery page a champion picture was to the right of it

the champion picter covered up the [X] to close masteries and wouldnt go away in turn i wasnt able to pick a champion and unintentionally dodged

i tried picking other mastery pages, saving/ deleting, moving my mouse around anything i could find to try to highlight another champion to get that to close but nothing worked.

fortunately i had just finished my series but -3lp will mean insta demote if i lose, such is life, but i do feel that if this happened to me in a serious series i would be heartbroken, as would mane others

thank you for your time