Fix #1038 by catching invalid cursor ranges

pv/storesession.cpp

@@ -145,6 +145,7 @@ bool StoreSession::start()
 	uint64_t end_sample;
 
 	if (sample_range_.first == sample_range_.second) {
+		// No sample range specified, save everything we have
 		start_sample_ = 0;
 		sample_count_ =	any_segment->get_sample_count();
 	} else {
@@ -159,6 +160,12 @@ bool StoreSession::start()
 		}
 	}
 
+	// Make sure the sample range is valid
+	if (start_sample_ > any_segment->get_sample_count()) {
+		error_ = tr("Can't save range without sample data.");
+		return false;
+	}
+
 	// Begin storing
 	try {
 		const auto context = session_.device_manager().context();

pv/toolbars/mainbar.cpp

@@ -612,6 +612,13 @@ void MainBar::export_file(shared_ptr<OutputFormat> format, bool selection_only)
 		const uint64_t end_sample = (uint64_t)max(
 			(double)0, end_time.convert_to<double>() * samplerate);
 
+		if ((start_sample == 0) && (end_sample == 0)) {
+			// Both cursors are negative and were clamped to 0
+			show_session_error(tr("Invalid Range"), tr("The cursors don't " \
+					"define a valid range of samples."));
+			return;
+		}
+
 		sample_range = make_pair(start_sample, end_sample);
 	} else {
 		sample_range = make_pair(0, 0);