correct bug null ptr

ChangeLog

 4.0.10 DD/MM/YYYY
 ------
+* Correct bug for null ptr in contruction of local setting directory
 
 4.0.9 19/05/2020
 -----

src/main/java/fr/ill/ics/util/ConfigManager.java

@@ -642,13 +642,15 @@ public class ConfigManager {
 	}
 
 	private static void setLocalFilesDirectory(String tmp) {
-		if (tmp.isEmpty() == false) {
-			if (!new File(tmp).exists()) {
-			// 	Directory does not exist: create it
-				File file = new File(tmp);
-				file.mkdir();
+		if (tmp != null) {
+			if (tmp.isEmpty() == false) {
+				if (!new File(tmp).exists()) {
+				// 	Directory does not exist: create it
+					File file = new File(tmp);
+					file.mkdir();
+				}
+				localFilesDirectory = tmp;
 			}
-			localFilesDirectory = tmp;
 		}
 	}
 }