Disable start button if no test types selected.
Disable start button if no test types selected.

wpt-on-tv-tf/wpt-tools,UprootStaging/wpt-tools,frewsxcv/wpt-tools,vivliostyle/wpt-tools,UprootStaging/wpt-tools,UprootStaging/wpt-tools,frewsxcv/wpt-tools,kaixinjxq/wpt-tools,vivliostyle/wpt-tools,kaixinjxq/wpt-tools,wpt-on-tv-tf/wpt-tools,wpt-on-tv-tf/wpt-tools,kaixinjxq/wpt-tools,frewsxcv/wpt-tools,vivliostyle/wpt-tools