diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index 5ee9a9f..8d42d03 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -2,7 +2,7 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:versionCode="138"
-    android:versionName="4.2.4a">
+    android:versionName="4.2.4b">
     <!-- android:allowBackup="false" -->
     <uses-permission android:name="android.permission.BLUETOOTH" />
     <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
diff --git a/app/src/main/java/uk/org/openseizuredetector/SdDataSourceBLE.java b/app/src/main/java/uk/org/openseizuredetector/SdDataSourceBLE.java
index 093c949..61c61c0 100644
--- a/app/src/main/java/uk/org/openseizuredetector/SdDataSourceBLE.java
+++ b/app/src/main/java/uk/org/openseizuredetector/SdDataSourceBLE.java
@@ -368,17 +368,21 @@ public class SdDataSourceBLE extends SdDataSource {
          * @param gattCharacteristic - the characteristic to be read.
          */
         private void executeReadCharacteristic(BluetoothGattCharacteristic gattCharacteristic) {
-            boolean retVal = mBluetoothGatt.readCharacteristic(gattCharacteristic);
-            if (retVal) {
-                Log.d(TAG, "executeReadCharacteristic - read initiated successfully");
+            if (gattCharacteristic != null) {
+                boolean retVal = mBluetoothGatt.readCharacteristic(gattCharacteristic);
+                if (retVal) {
+                    Log.d(TAG, "executeReadCharacteristic - read initiated successfully");
+                } else {
+                    Log.d(TAG, "executeReadCharacteristic - read initiation failed - waiting, then re-trying");
+                    mHandler.postDelayed(new Runnable() {
+                        public void run() {
+                            Log.w(TAG, "Executing delayed read of characteristic");
+                            executeReadCharacteristic(gattCharacteristic);
+                        }
+                    }, 100);
+                }
             } else {
-                Log.d(TAG, "executeReadCharacteristic - read initiation failed - waiting, then re-trying");
-                mHandler.postDelayed(new Runnable() {
-                    public void run() {
-                        Log.w(TAG, "Executing delayed read of characteristic");
-                        executeReadCharacteristic(gattCharacteristic);
-                    }
-                }, 100);
+                Log.i(TAG,"ExecuteReadCharacteristic() - gatCharacteristic is null, so not doing anything");
             }
         }