pavuapplication: initialize members in the constructor

It seems that without explicit initialization of the members they remain
uninitialized. The lack of initialization caused crashing, because
PavuApplication::on_activate() creates the MainWindow only if mainWindow
is NULL, and if it's some random value instead, on_activate() calls
selectTab() on a non-existent window.

Fixes: https://gitlab.freedesktop.org/pulseaudio/pavucontrol/issues/49

src/pavuapplication.cc

@@ -30,7 +30,14 @@
 #include "pavucontrol.h"
 #include "mainwindow.h"
 
-PavuApplication::PavuApplication() : Gtk::Application("org.pulseaudio.pavucontrol", Gio::ApplicationFlags::APPLICATION_HANDLES_COMMAND_LINE) {
+PavuApplication::PavuApplication() :
+    Gtk::Application("org.pulseaudio.pavucontrol", Gio::ApplicationFlags::APPLICATION_HANDLES_COMMAND_LINE),
+    mainWindow(NULL),
+    retry(false),
+    maximize(false),
+    tab(0),
+    version(false),
+    m(NULL) {
 }
 
 /*

src/pavuapplication.h

@@ -45,7 +45,7 @@ private:
     MainWindow* create_window();
     void on_hide_window(Gtk::Window* window);
 
-    pa_glib_mainloop *m = NULL;
+    pa_glib_mainloop *m;
 };