MSI does not support "Remove if empty" on installation
MSI does not support the installation action Remove if empty for registry keys. To work around this limitation, InstallMate replaces this action by Create on demand. However, this might not always be appropriate.
MSI only supports a subset of the generally available installation and removal actions offered by InstallMate. Moreover, the available MSI subset depends on the object type.
If Create on demand is an acceptable substitute, you can ignore this message. Otherwise, select a different installation action; see Registry keys to check which actions are supported by MSI. Alternatively, build an InstallMate installer instead.
InstallMate versus Windows Installer