fix NullPointerException when attribute key is defined and value is set to null, caused by calling .toString() on null.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/main/java/org/traccar/model/ExtendedModel.java b/src/main/java/org/traccar/model/ExtendedModel.java
index 6a4f502f7..d3d247fdd 100644
--- a/src/main/java/org/traccar/model/ExtendedModel.java
+++ b/src/main/java/org/traccar/model/ExtendedModel.java
@@ -90,7 +90,7 @@ public class ExtendedModel extends BaseModel {
     }
 
     public String getString(String key, String defaultValue) {
-        if (attributes.containsKey(key)) {
+        if (attributes.containsKey(key) && attributes.get(key) != null) {
             return attributes.get(key).toString();
         } else {
             return defaultValue;