DBusErrorHandlerI: add virtual destructor

This prevents a "new-delete-type-mismatch" detection by ASAN when
quitting a client due to the unique_ptr trying to use the default
deleter.

Change-Id: I5ba85f480ec420947c20b8167aab8c4bcffe78f7
Tuleap: #405

src/interfaces/dbuserrorhandleri.h

@@ -28,6 +28,8 @@ namespace Interfaces {
  */
 class DBusErrorHandlerI {
 public:
+    virtual ~DBusErrorHandlerI() = default;
+
     virtual void connectionError(const QString& error) = 0;
     virtual void invalidInterfaceError(const QString& error) = 0;
 };