mpv: fix errors related to m_mpv initialization

Signed-off-by: Mavridis Philippe <mavridisf@gmail.com>

kaffeine/src/player-parts/libmpv-part/libmpv_part.cpp

@@ -66,6 +66,7 @@ K_EXPORT_COMPONENT_FACTORY (libmpvpart, MpvPartFactory);
 
 MpvPart::MpvPart(TQWidget* parentWidget, const char* widgetName, TQObject* parent, const char* name, const TQStringList& /*args*/)
     : KaffeinePart(parent, name ? name : "MpvPart"),
+      m_mpv(nullptr),
       m_current(0),
       m_seeking(false),
       m_seekpos(0),
@@ -430,6 +431,8 @@ void MpvPart::slotPlay() {
 }
 
 void MpvPart::slotPause(bool pause) {
+    if (!m_mpv) return;
+
     int value = pause ? 1 : 0;
     mpv_set_property(m_mpv, "pause", MPV_FORMAT_FLAG, &value);
     stateChanged(pause ? "paused" : (isStream() ? "playing_stream" : "playing_file"));
@@ -528,6 +531,8 @@ void MpvPart::slotSetSeekingPos(int percent) {
 }
 
 uint MpvPart::volume() const {
+    if (!m_mpv) return 0;
+
     int64_t value = 0;
     mpv_get_property(m_mpv, "ao-volume", MPV_FORMAT_INT64, &value);
     return value;
@@ -572,7 +577,7 @@ void MpvPart::slotNext() {
 }
 
 void MpvPart::slotStop() {
-    if (!isPlaying()) {
+    if (!m_mpv || !isPlaying()) {
         return;
     }
 
@@ -584,11 +589,13 @@ void MpvPart::slotStop() {
 }
 
 void MpvPart::slotMute() {
+    if (!m_mpv) return;
     int value = isMute() ? 0 : 1;
     mpv_set_property(m_mpv, "ao-mute", MPV_FORMAT_FLAG, &value);
 }
 
 void MpvPart::slotReloadSubtitles() {
+    if (!m_mpv) return;
     TQStringList subtitles = m_mrl.subtitleFiles();
     int subId = m_mrl.currentSubtitle();
 
@@ -615,6 +622,8 @@ void MpvPart::slotToggleRecording() {
 }
 
 void MpvPart::startRecording() {
+    if (!m_mpv) return;
+
     // Ensure we have an out file and start recording
     if (m_recordFilePath.isEmpty()) {
         slotSetRecordingFile();
@@ -630,6 +639,7 @@ void MpvPart::startRecording() {
 }
 
 void MpvPart::stopRecording() {
+    if (!m_mpv) return;
     mpv_set_property_string(m_mpv, "stream-record", "");
     m_recordAction->setChecked(false);
 }
@@ -768,6 +778,8 @@ void MpvPart::hideContextMenu() {
     mpv_free_node_contents(&result);
 
 void MpvPart::slotShot() {
+    if (!m_mpv) return;
+
     mpv_node result;
     int w, h, stride;
     char *format;