QKdeTheme: Don't leak resources on shutdown

The theme stores an array of pointers to allocated QFonts, which need to
be freed.

While this is not a "hard" leak (the OS will clean up the memory on
shutdown, and QKdeTheme lives as long as the application), it creates
ASAN warnings, which distract from more severe issues.

Change-Id: Iaa57138e5273c300c616ba85340283f18a267b09
Reviewed-by: Piotr Wierciński <piotr.wiercinski@qt.io>

src/gui/platform/unix/qkdetheme.cpp

@@ -67,6 +67,7 @@ public:
     };
 
     QKdeThemePrivate(const QStringList &kdeDirs, int kdeVersion);
+    ~QKdeThemePrivate() { clearResources(); }
 
     static QString kdeGlobals(const QString &kdeDir, int kdeVersion)
     {