Remove redundant initialization

src/engine/gstengine.cpp

@@ -72,8 +72,7 @@ const char *GstEngine::kDirectSoundSink = "directsoundsink";
 const char *GstEngine::kOSXAudioSink = "osxaudiosink";
 
 GstEngine::GstEngine(TaskManager *task_manager)
-    : Engine::Base(),
-      task_manager_(task_manager),
+    : task_manager_(task_manager),
       buffering_task_id_(-1),
       latest_buffer_(nullptr),
       stereo_balancer_enabled_(false),

src/engine/vlcengine.cpp

@@ -39,8 +39,7 @@
 #include "vlcscopedref.h"
 
 VLCEngine::VLCEngine(TaskManager *task_manager)
-  : EngineBase(),
-    instance_(nullptr),
+  : instance_(nullptr),
     player_(nullptr),
     state_(Engine::Empty) {
 

src/playlist/playlistdelegates.cpp

@@ -363,7 +363,7 @@ QWidget *TextItemDelegate::createEditor(QWidget *parent, const QStyleOptionViewI
   return new QLineEdit(parent);
 }
 
-TagCompletionModel::TagCompletionModel(CollectionBackend *backend, Playlist::Column column) : QStringListModel() {
+TagCompletionModel::TagCompletionModel(CollectionBackend *backend, Playlist::Column column) {
 
   QString col = database_column(column);
   if (!col.isEmpty()) {