Prevent crashing when asking for status with invalid pid

The application (or a thread) crashes silently when the DBus functions status or refresh_status are called with an invalid Pid

service.py

@@ -47,14 +47,21 @@ class RWAService(dbus.service.Object):
         self._update_session(pid)
         return self._get_status(pid)
 
-    @dbus.service.method("org.ArcticaProject.RWA", in_signature="i")
+    @dbus.service.method("org.ArcticaProject.RWA", in_signature="i", out_signature="s")
     def stop(self, pid: int):
         """Stop a remote session."""
-        session = self.sessions[pid]
+        try:
+            session = self.sessions[pid]
+        except KeyError:
+            return json.dumps({"pid": pid, "status": "stopped"}, sort_keys=True)
         session.stop()
+        return json.dumps({"id": pid, "status": "stopped"}, sort_keys=True)
 
     def _get_status(self, pid: int) -> str:
-        session = self.sessions[pid]
+        try:
+            session = self.sessions[pid]
+        except KeyError:
+            return json.dumps({"id": pid, "status": "dead"}, sort_keys=True)
         return json.dumps(session.status)
 
     def _ensure_update_service(self):
@@ -65,7 +72,13 @@ class RWAService(dbus.service.Object):
 
     def _update_session(self, pid: int):
         """Update the status of a session."""
-        session = self.sessions[pid]
+        try:
+            session = self.sessions[pid]
+        except KeyError:
+            print(f"Session #{pid}")
+            print("Session is dead.")
+            return
+
         print(f"Session #{session.pid}")
 
         # Check if VNC process is still running