Handling quat_corr== null

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

@@ -8446,11 +8446,15 @@ public class Interscene {
 		if (debugLevel > -3) {
 			System.out.println("getQuaternionCorrection(): Current  ref_scene.getQuatCorr()=["+
 					quat_corr0[0]+", "+quat_corr0[1]+", "+quat_corr0[2]+", "+quat_corr0[3]+"]");
+			if (quat_corr == null) {
+				System.out.println("getQuaternionCorrection(): quat_corr==null");
+			} else {
 				System.out.println("getQuaternionCorrection(): Differential correction=         ["+
 						quat_corr [0]+", "+quat_corr [1]+", "+quat_corr [2]+", "+quat_corr [3]+"]");
 				System.out.println("getQuaternionCorrection(): Combined  correction=            ["+
 						quat_corr1[0]+", "+quat_corr1[1]+", "+quat_corr1[2]+", "+quat_corr1[3]+"]");
 			}
+		}
 		return quat_corr1; // new combined correction
     }