session: make sure signals set is initialized

This fixes parts of bug #387.

diff --git a/pv/session.cpp b/pv/session.cpp
index ef1159ee599f8abfbf0a7e6b90d6c100eeef3f44..0ac5bb7286dbe2cd6c76dbd07ca967ec2d289176 100644 (file)
--- a/pv/session.cpp
+++ b/pv/session.cpp
@@ -579,6 +579,10 @@ void Session::feed_in_analog(shared_ptr<Analog> analog)
        const float *data = static_cast<const float *>(analog->data_pointer());
        bool sweep_beginning = false;
 
+       if (signals_.empty()) {
+               update_signals();
+       }
+
        for (auto channel : channels)
        {
                shared_ptr<data::AnalogSegment> segment;