"Unrecognized variables in the Ivy settings file ${workspace_loc:ProjectA/ivysettings.xml}" when property file not exists

Under Preferences -> Ivy -> Settings I set the "Ivy settings path:" which exists and under "Property files:" two property files.

The property files are configured as:
${workspace_loc:ProjectA/global.properties}
${workspace_loc:ProjectA/local.properties}

The first property file exists. The second one not. I need this behaviour because we share this settings in our company and some developer need the local.properties to override properties.

Because Eclipse could not substitute the property config ${workspace_loc:ProjectA/local.properties} so an "Unrecognized variables in the Ivy settings file ${workspace_loc:ProjectA/ivysettings.xml}" error. When I set the property file as ${workspace_loc:ProjectA}/local.properties I get no error but an "File not found" in an other class.

I fixed this issue and attached an patch.