db/simple: use C++11 initializer

src/db/plugins/simple/SimpleDatabasePlugin.cxx

@@ -60,8 +60,7 @@ inline SimpleDatabase::SimpleDatabase(const ConfigBlock &block)
 #ifdef ENABLE_ZLIB
 	 compress(block.GetBlockValue("compress", true)),
 #endif
-	 cache_path(block.GetPath("cache_directory")),
-	 prefixed_light_song(nullptr)
+	 cache_path(block.GetPath("cache_directory"))
 {
 	if (path.IsNull())
 		throw std::runtime_error("No \"path\" parameter specified");

src/db/plugins/simple/SimpleDatabasePlugin.hxx

@@ -58,7 +58,7 @@ class SimpleDatabase : public Database {
 	 * A buffer for GetSong() when prefixing the #LightSong
 	 * instance from a mounted #Database.
 	 */
-	mutable PrefixedLightSong *prefixed_light_song;
+	mutable PrefixedLightSong *prefixed_light_song = nullptr;
 
 	/**
 	 * A buffer for GetSong().