default Filter ctor

src/Filter.cpp

@@ -38,6 +38,9 @@ void safeReleaseFilter(Filter **ppFilter)
     *ppFilter = 0;
 }
 
+Filter::Filter()
+{}
+
 Filter::Filter(FilterPrivate &d)
     :DPTR_INIT(&d)
 {

src/QtAV/Filter.h

@@ -60,6 +60,7 @@ class Q_EXPORT Filter
 {
     DPTR_DECLARE_PRIVATE(Filter)
 public:
+    Filter();
     virtual ~Filter();
     //isEnabled() then setContext
     //TODO: parameter FrameContext