more cuas debugging

src/main/java/com/elphel/imagej/tileprocessor/OpticalFlow.java

@@ -4440,7 +4440,12 @@ public class OpticalFlow {
 		}
 		// read DSI_MAIN
 		double [][] dsi = quadCLT_ref.readDsiMain();
-		quadCLT_ref.setDSI(dsi); // was not here! (11/26/2022)
+		if (dsi != null) {
+			quadCLT_ref.setDSI(dsi); // was not here! (11/26/2022)
+		} else {
+			quadCLT_ref.readComboDSI(true);
+			dsi = quadCLT_ref.dsi;
+		}
 		double [][] combo_dsi = null;
 		if (dsi[TwoQuadCLT.DSI_SPREAD_AUX] == null) {
 			System.out.println("DSI_MAIN file has old format and does not have spread data, will recalculate.");