Complete backward compatibility which has a bug in commit 6bd4ca1af3

src/main/java/altk/comm/engine/Broadcast.java

@@ -1502,6 +1502,7 @@ public abstract class Broadcast
 	 * @return false if no change
 	 */
 	private boolean setOperatingHours(String timeParam, String value) {
+		if (value == null || value.trim().length() == 0) return false;
 		String timeOfDay = CommEngine.checkTimeOfDay(value);
 		if (timeOfDay == null) throw new RuntimeException(String.format("Invalid value for %s: %s", timeParam, value));
 		switch (timeParam) {