Qt: fix uninitialized members (UNINIT_CTOR) reported by Coverity (CID 1228882)

Change-Id: I1f09fa9a8421e702d2fff963afc899617f2e6222
Reviewed-on: https://code.wireshark.org/review/10794
Reviewed-by: Pascal Quantin <pascal.quantin@gmail.com>

ui/qt/wireshark_application.cpp

@@ -482,7 +482,8 @@ WiresharkApplication::WiresharkApplication(int &argc,  char **argv) :
     QApplication(argc, argv),
     initialized_(false),
     is_reloading_lua_(false),
-    active_captures_(0)
+    active_captures_(0),
+    if_notifier_(NULL)
 {
     wsApp = this;
     setApplicationName("Wireshark");