refactor: check for valid episode number

ani-cli

@@ -308,6 +308,7 @@ while :; do
 		s)	printf "${c_blue}Choose episode $c_cyan[1-%d]$c_reset:$c_green " $last_ep_number
 			read episode
 			printf "$c_reset"
+			[ "$episode" -eq "$episode" ] 2>/dev/null || die "Invalid number entered"
 			;;
 
 		q)