[FIX][I] Stop session when current project is closed

Stops the current session when the current project is closed. This is
done as the session state is dropped at that point, meaning we can no
longer work with the old session.

Furthermore, dropping the old session should guarantee that we don't
have any references to resources of the closed project. This is
necessary as trying to access these resources would lead to an assertion
error.

de.fu_berlin.inf.dpp.intellij/src/de/fu_berlin/inf/dpp/intellij/SarosComponent.java

@@ -4,9 +4,14 @@
 import com.intellij.openapi.keymap.Keymap;
 import com.intellij.openapi.keymap.KeymapManager;
 import com.intellij.openapi.project.Project;
+import de.fu_berlin.inf.dpp.session.ISarosSession;
+import de.fu_berlin.inf.dpp.session.ISarosSessionManager;
+import de.fu_berlin.inf.dpp.session.SessionEndReason;
+import de.fu_berlin.inf.dpp.util.ThreadUtils;
 import java.awt.event.KeyEvent;
 import java.io.InputStream;
 import javax.swing.KeyStroke;
+import org.apache.log4j.Logger;
 import org.apache.log4j.PropertyConfigurator;
 import org.apache.log4j.helpers.LogLog;
 import org.jetbrains.annotations.NotNull;
@@ -17,9 +22,13 @@
  */
 public class SarosComponent implements com.intellij.openapi.components.ProjectComponent {
 
+  private static final Logger log = Logger.getLogger(SarosComponent.class);
+
   /** This is the plugin ID that identifies the saros plugin in the IDEA ecosystem. */
   public static final String PLUGIN_ID = "de.fu_berlin.inf.dpp.intellij";
 
+  private IntellijProjectLifecycle intellijProjectLifecycle;
+
   public SarosComponent(final Project project) {
     loadLoggers();
 
@@ -47,7 +56,9 @@ public SarosComponent(final Project project) {
       LogLog.error("could not load saros property file 'saros.properties'", e);
     }
 
-    IntellijProjectLifecycle.getInstance(project).start();
+    intellijProjectLifecycle = IntellijProjectLifecycle.getInstance(project);
+
+    intellijProjectLifecycle.start();
   }
 
   public static boolean isSwtBrowserEnabled() {
@@ -94,6 +105,16 @@ public void projectOpened() {
 
   @Override
   public void projectClosed() {
-    // TODO: Update project
+    ISarosSessionManager sarosSessionManager =
+        intellijProjectLifecycle.getSarosContext().getComponent(ISarosSessionManager.class);
+
+    ISarosSession currentSession = sarosSessionManager.getSession();
+
+    if (currentSession != null) {
+      ThreadUtils.runSafeAsync(
+          "StopSession",
+          log,
+          () -> sarosSessionManager.stopSession(SessionEndReason.LOCAL_USER_LEFT));
+    }
   }
 }