Since it's possible to install the driver without knowing the path to the SteamVR folder to get the vrpathreg binary, not being able to parse where SteamVR is installed should still allow for installation to go on.
If anything, replacing the check with one that ensures openvrpaths.vrpath exists seems like a more reliable option. Since this is actually what we're really looking for.
In a case like this, a variable should be set to stop the installer from attempting the removal of manually copied drivers to avoid errors.
Since it's possible to install the driver without knowing the path to the SteamVR folder to get the vrpathreg binary, not being able to parse where SteamVR is installed should still allow for installation to go on.
If anything, replacing the check with one that ensures openvrpaths.vrpath exists seems like a more reliable option. Since this is actually what we're really looking for.
In a case like this, a variable should be set to stop the installer from attempting the removal of manually copied drivers to avoid errors.