Don't switch to invisible first/last room on Ctrl+PgUp/PgDn

If you're on the first visible room and try to switch to the previous
one (or on the last visible room switching to the next one), the first
(or last) room in the list is incorrectly selected even if it's not
currently visible.

Fix this by not first entering each room and then checking whether it is
the one we really wanted, but iterating until we find a room that we
want and only entering it then.

src/qml/Page/RoomListPage.qml

@@ -132,17 +132,25 @@ Kirigami.ScrollablePage {
     }
 
     function goToNextRoom() {
-        do {
-            listView.incrementCurrentIndex();
-        } while (!listView.currentItem.visible && listView.currentIndex !== listView.count - 1)
-        listView.currentItem.action.trigger();
+        let index = listView.currentIndex;
+        while (index++ !== listView.count - 1) {
+            if (listView.itemAtIndex(index).visible) {
+                listView.currentIndex = index;
+                listView.currentItem.action.trigger();
+                return;
+            }
+        }
     }
 
     function goToPreviousRoom() {
-        do {
-            listView.decrementCurrentIndex();
-        } while (!listView.currentItem.visible && listView.currentIndex !== 0)
-        listView.currentItem.action.trigger();
+        let index = listView.currentIndex;
+        while (index-- !== 0) {
+            if (listView.itemAtIndex(index).visible) {
+                listView.currentIndex = index;
+                listView.currentItem.action.trigger();
+                return;
+            }
+        }
     }
 
     titleDelegate: collapsedMode ? empty : searchField