MacOS – Problem With the Click Command – AppleScript

I'm trying to do some GUI scripting with AppleScript but every time I try to use the click command, it will work but cause an error. If I use a try statement it works fine, but I shouldn't have to do that. Here's some code that I started to turn on Speakable Items:

tell application "System Preferences"
    set current pane to pane id "com.apple.preference.universalaccess"
    reveal anchor "SpeakableItems" of current pane
end tell

tell application "System Events"
    click radio button "On" of radio group of tab group 1 of window 1 of application process "System Preferences"
end tell

The 'On' radio button gets clicked, but I get this error aswell:

error "System Events got an error: radio button \"On\" of radio group of tab group 1 of window 1 of application process \"System Preferences\" doesn’t understand the “click” message." number -1708 from radio button "On" of radio group of tab group 1 of window 1 of application process "System Preferences"

Can someone tell me what I'm doing wrong?