altosui/telegps: Display error message when attempting to graph unknown files

Instead of presenting an empty graph window.

Signed-off-by: Keith Packard <keithp@keithp.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/altoslib/AltosTelemetryFile.java b/altoslib/AltosTelemetryFile.java
index 679c6809..01d82c24 100644
--- a/altoslib/AltosTelemetryFile.java
+++ b/altoslib/AltosTelemetryFile.java
@@ -117,6 +117,10 @@ public class AltosTelemetryFile implements AltosRecordSet {
 		return cal_data;
 	}
 
+	public boolean valid() {
+		return true;
+	}
+
 	public void capture_series(AltosDataListener listener) {
 		AltosCalData	cal_data = cal_data();