Please address the comments from this code review:

## Overall Comments
- In TrayWidget::showEvent you guard against a null m_handler but still unconditionally call window()->installEventFilter and window()->setMouseTracking; consider also checking that window() is non-null before using it to avoid potential crashes during early lifecycle.
- In SniTrayProtocolHandler::eventFilter, window()->windowHandle() is called before any null check on window(); if window() can be null in some cases, add a guard for window() itself before dereferencing it to prevent rare null-dereference crashes.

## Individual Comments

### Comment 1
<location path="plugins/application-tray/sniprotocolhandler.cpp" line_range="331" />
<code_context>

-                auto widget = static_cast<QWidget*>(parent());
-                auto plugin = Plugin::EmbedPlugin::get(widget->window()->windowHandle());
+                auto *win = window()->windowHandle();
+                if (!win)
+                    return false;
</code_context>
<issue_to_address>
**issue (bug_risk):** Guard against a potential nullptr from window() before calling windowHandle().

`window()` might return `nullptr` depending on when this is called. To avoid a potential null dereference, first store the result in a local variable, check it, and only then access `windowHandle()`, e.g. `auto *w = window(); if (!w) return false; auto *win = w->windowHandle();` to match the defensive pattern used for `win` below.
</issue_to_address>

### Comment 2
<location path="plugins/application-tray/traywidget.cpp" line_range="48-55" />
<code_context>
 void TrayWidget::showEvent(QShowEvent* event)
 {
     Q_UNUSED(event)
+    if (!m_handler)
+        return;
+
     m_handler->setWindow(window());
     window()->installEventFilter(m_handler);
     window()->setMouseTracking(true);
</code_context>
<issue_to_address>
**suggestion (bug_risk):** Avoid repeatedly installing the same event filter on each showEvent.

`window()->installEventFilter(m_handler)` runs on every show, and Qt will invoke the filter once per installation, causing duplicate handling per event. Please ensure the filter is installed only once (e.g., track an `installed` flag, detect `window()` changes, or move installation to a place that runs only once when the window becomes available).

Suggested implementation:

```cpp
void TrayWidget::showEvent(QShowEvent* event)
{
    Q_UNUSED(event)

    if (!m_handler)
        return;

    QWidget *w = window();
    if (!w)
        return;

    m_handler->setWindow(w);

    if (m_lastWindowWithFilter != w) {
        w->installEventFilter(m_handler);
        m_lastWindowWithFilter = w;
    }

    w->setMouseTracking(true);

```

1. In `traywidget.h`, add a member to track the last window where the filter was installed, e.g.:
   `QWidget *m_lastWindowWithFilter = nullptr;`
2. Ensure `m_lastWindowWithFilter` is initialized to `nullptr` in the constructor if in-class initialization is not used.
</issue_to_address>