Add virtual destructors to base classes

src/actions.h

@@ -190,6 +190,8 @@ struct BaseAction
 {
 	BaseAction(Type type_, const char *name_): m_name(name_), m_type(type_) { }
 
+	virtual ~BaseAction() { }
+
 	const std::string &name() const { return m_name; }
 	Type type() const { return m_type; }
 	

src/lyrics_fetcher.h

@@ -30,6 +30,8 @@ struct LyricsFetcher
 {
 	typedef std::pair<bool, std::string> Result;
 
+	virtual ~LyricsFetcher() { }
+
 	virtual const char *name() const = 0;
 	virtual Result fetch(const std::string &artist, const std::string &title);