Product Version = NetBeans IDE 8.1 (Build 201510222201)
Operating System = Windows 7 version 6.1 running on amd64
Java; VM; Vendor = 1.8.0_66
Runtime = Java HotSpot(TM) 64-Bit Server VM 25.66-b18

Reproducibility: Happens every time

STEPS:
  1. Open a maven multi-module project
  2. Go to Source -> Inspect.. 
  3. Select current project as scope (the current project is the maven multi-module project)
  4. Select a single inspection (for example unnecessary unboxing)  and then click on the button "Inspect"

ACTUAL:
  The inspection result is empty because a maven multi-module project is an empty project. It only contains references to its sub-projects.

EXPECTED:
  The inspection is executed recursively on the project, on its sub-project on their sub-sub-project and so on. In the end a global result about all the occurrences in all the projects is provided.

POSSIBLE WORKAROUND:
  In the "scope" field there is the option "all opened projects". Maybe when the inspector is executed on a multi-module project it can get the references of all the submodules and then use the algorithm used for "all opened project" passing this set of sub-projects instead of the set of opened projects.