fixed segfault in edit button

src/editsample.cpp

@@ -30,6 +30,10 @@ EditSample::EditSample(const std::string& audioFile_, QWidget *parent) : QDialog
 }
 
 EditSample::~EditSample() {
+	// here was a race condition: when the sample is played and the current possition is updated
+	// after this object is destroyed there will be a segfault.
+	stop();
+
 	delete ui;
 }