Clear both cursor caches

Summary: There are two cursor caches: m_cursors and m_cursorsByName. The second doesn't ever seem to be cleared.

Reviewers: #kwin, davidedmundson, graesslin

Reviewed By: #kwin, graesslin

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D12542

pointer_input.cpp

@@ -908,6 +908,7 @@ CursorImage::CursorImage(PointerInputRedirection *parent)
         connect(m_cursorTheme, &WaylandCursorTheme::themeChanged, this,
             [this] {
                 m_cursors.clear();
+                m_cursorsByName.clear();
                 loadThemeCursor(Qt::ArrowCursor, &m_fallbackCursor);
                 updateDecorationCursor();
                 updateMoveResize();