android: LOKitThread::refresh: Add null check

This fixes as another crash with Android Viewer that
could (ocassionaly) be observed by

* open some ODT document
* press the "back button" while the document is still
being loaded
* repeat steps 1-2 until the crash occurs

Corresponding 'adb logcat' output:

I LibreOfficeMainActivity: onDestroy..
I LOKitTileProvider: Document destroyed: /storage/emulated/0/Download/simple.odt
D LOKitThread: mTileProvider==null when calling updatePartPageRectangles
D AndroidRuntime: Shutting down VM
E AndroidRuntime: FATAL EXCEPTION: main
E AndroidRuntime: Process: org.libreoffice, PID: 9190
E AndroidRuntime: java.lang.NullPointerException: Attempt to invoke interface method 'boolean org.libreoffice.TileProvider.isSpreadsheet()' on a null object reference
E AndroidRuntime:        at org.libreoffice.LOKitThread.refresh(LOKitThread.java:159)
E AndroidRuntime:        at org.libreoffice.LOKitThread.access$000(LOKitThread.java:26)
E AndroidRuntime:        at org.libreoffice.LOKitThread$1.run(LOKitThread.java:239)
E AndroidRuntime:        at android.os.Handler.handleCallback(Handler.java:883)
E AndroidRuntime:        at android.os.Handler.dispatchMessage(Handler.java:100)
E AndroidRuntime:        at android.os.Looper.loop(Looper.java:214)
E AndroidRuntime:        at android.app.ActivityThread.main(ActivityThread.java:7356)
E AndroidRuntime:        at java.lang.reflect.Method.invoke(Native Method)
E AndroidRuntime:        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
E AndroidRuntime:        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)

Change-Id: I9787a13b3485a87a133f8b5e4e03bbf3618fb2f0
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/90089
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

1 files changed, 1 insertions, 1 deletions

diff --git a/android/source/src/java/org/libreoffice/LOKitThread.java b/android/source/src/java/org/libreoffice/LOKitThread.java
index 2031b95e25f8..9c216b54fb1f 100644
--- a/android/source/src/java/org/libreoffice/LOKitThread.java
+++ b/android/source/src/java/org/libreoffice/LOKitThread.java
@@ -156,7 +156,7 @@ class LOKitThread extends Thread {
         mLayerClient.clearAndResetlayers();
         redraw();
         updatePartPageRectangles();
-        if (mTileProvider.isSpreadsheet()) {
+        if (mTileProvider != null && mTileProvider.isSpreadsheet()) {
             updateCalcHeaders();
         }
     }