gui: Fix flags on playlist manager tab

I wasn't initializing the variable, so it was sometimes drawing buttons
next to the filter entry bar.

Signed-off-by: Anna Schumaker <schumaker.anna@gmail.com>

gui/tabs.cpp

@@ -286,6 +286,7 @@ OcarinaPage::OcarinaPage(Playqueue *pq, unsigned int flags, unsigned int pg)
 
 OcarinaPage::OcarinaPage(const std::string &name, const std::string &icon,
 			 Playqueue *pq)
+	    : init_flags(0)
 {
 	ManagerTab *man_tab = new ManagerTab(name, icon);
 	tab = man_tab;