LibWeb: Do not clear the selection, when query is not found

Fixes #4743

Libraries/LibWeb/Page/Page.cpp

@@ -726,11 +726,11 @@ Page::FindInPageResult Page::find_in_page_previous_match()
 
 void Page::update_find_in_page_selection(Vector<GC::Root<DOM::Range>> matches)
 {
-    clear_selection();
-
     if (matches.is_empty())
         return;
 
+    clear_selection();
+
     auto current_range = matches[m_find_in_page_match_index];
     auto common_ancestor_container = current_range->common_ancestor_container();
     auto& document = common_ancestor_container->document();

Tests/LibWeb/Text/expected/HTML/Window-find-mutations.txt

@@ -1,3 +1,4 @@
 Selection: [object Text] 0 - [object Text] 6
 Selection: [object Text] 0 - [object Text] 3
+Selection: [object Text] 0 - [object Text] 3
 Expected exception: IndexSizeError: Selection.getRangeAt() on empty Selection or with invalid argument

Tests/LibWeb/Text/input/HTML/Window-find-mutations.html

@@ -16,6 +16,11 @@ test(() => {
     document.querySelector('div').childNodes[0].deleteData(3, 3);
     showSelection();
 
+    // Try to find 'baz'.
+    window.find('baz');
+    // Selection should be untouched, since 'baz' was not found
+    showSelection();
+
     // Try to find 'bar'.
     getSelection().empty();
     window.find('bar');