LibWeb: Ensure a repaint occurs when the current selection is cleared

This fixes an issue where clearing the find in page query would not
always visually clear the selection.

(cherry picked from commit 0b33331f3678eb69bc3448949dfc2c1e1e7671e6)

Userland/Libraries/LibWeb/DOM/Range.cpp

@@ -96,13 +96,14 @@ void Range::set_associated_selection(Badge<Selection::Selection>, JS::GCPtr<Sele
 
 void Range::update_associated_selection()
 {
-    if (!m_associated_selection)
-        return;
-    if (auto* viewport = m_associated_selection->document()->paintable()) {
+    if (auto* viewport = m_start_container->document().paintable()) {
         viewport->recompute_selection_states();
         viewport->set_needs_display();
     }
 
+    if (!m_associated_selection)
+        return;
+
     // https://w3c.github.io/selection-api/#selectionchange-event
     // When the selection is dissociated with its range, associated with a new range or the associated range's boundary
     // point is mutated either by the user or the content script, the user agent must queue a task on the user interaction