I have recently installed the latest Jenkins and started configuring it from scratch. To achieve a more consistent way of configuring tools on nodes, I am defining all the tools I have under Manage Jenkins > Global Tools Configuration but leave the paths blank. After that, on master I would add the tool located in the Tool Locations section under Manage Jenkins > Configure System. However when I test my job that uses one of the tools, it will fail saying that the tool location is null, thus indicating that the tool location in Configure System is not overriding those of the global tool configuration like how it works on slave systems.

To reproduce the problem:

1. In Global Tool Configuration page, create an entry for Ant by giving it a name (e.g. apache-ant-1.9.7) but leave the path blank.
2. In Configure System page, add the above entry and provide an actual installation path for Ant 1.9.7 under tool locations.
3. Create a job that invokes Ant, with the entry above, as a build step.
4. Run the job. At this point, it will fail saying that path is null.