Cope with none sloeber projects in the workspace

The listener fires Sloeber stuff but that will fail if the project is
not a sloeber project.

Author: jantje

io.sloeber.core/src/io/sloeber/core/listeners/resourceChangeListener.java

@@ -52,7 +52,13 @@ protected IStatus run(IProgressMonitor monitor) {
                     public void run(IProgressMonitor monitor) throws CoreException {
                         for (IProject curProject : changedSloeberCfgFiles) {
                             SloeberProject curSloeberProject = SloeberProject.getSloeberProject(curProject, false);
-                            curSloeberProject.sloeberCfgChanged();
+                            if (curSloeberProject == null) {
+                                // this is not a sloeber project;
+                                //make it one?
+                            }
+                            else{
+                                curSloeberProject.sloeberCfgChanged();
+                            }
                         }
                     }
                 };