From 513256854ec3eb21b86b14668cddcb6e3db2cdf2 Mon Sep 17 00:00:00 2001
From: Leland Lucius <github@homerow.net>
Date: Mon, 27 Apr 2015 20:28:41 -0500
Subject: [PATCH] Fix for bug #906

---
 src/effects/Contrast.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/effects/Contrast.cpp b/src/effects/Contrast.cpp
index d38e942c2..4c95b556b 100644
--- a/src/effects/Contrast.cpp
+++ b/src/effects/Contrast.cpp
@@ -102,6 +102,12 @@ float ContrastDialog::GetDB()
    AudacityProject *p = GetActiveProject();
    TrackListOfKindIterator iter(Track::Wave, p->GetTracks());
    Track *t = iter.First();
+   if(!t)
+   {
+      wxMessageDialog m(NULL, _("No wave tracks exist."), _("Error"), wxOK);
+      m.ShowModal();
+      return 1234.0; // 'magic number', but the whole +ve dB range will 'almost' never occur
+   }
    if(mT0 > mT1)
    {
       wxMessageDialog m(NULL, _("Start time after end time!\nPlease enter reasonable times."), _("Error"), wxOK);