Accidental refresh might block user in DW before repair step

Steps to reproduce:

• Setup a 4.1.4 XEM wiki (Tomcat + MySQL)
• Start and manually import XAR
• Shutdown and replace the WAR with a 5.2.1 or 5.3 M2
• Start, DW kicks in.
• Select "Yes, this is an upgrade"
• Select version 4.1.4 from the dropdown
• Click "Yes, this is it"
• Now the Repair button appears. Do NOT click it.
• Instead, press F5 or the corresponding shortcut key to refresh the page
• You are redirected back to choose "Yes, this is an upgrade"/"No, this is a new install"
• Click again on "Yes, this is an upgrade"
• you will see that the dropdown and "Yes, this is it" are disabled/grayed out, leaving the user no way to continue with the Upgrade.

I personally had to restart my wiki in order to clear this.