android: LibreOfficeMainActivity::onStop: Add null check

'mTileProvider' can be null here, e.g. while loading the document.

This fixes a crash that could be reproduced e.g. by

* open a document
* press the "back button" while the document is still
being loaded

(Most easily reproducibly right after app installation, since
loading the first doc takes a very long time then.)

Relevant log messages from `adb logcat` output:

E AndroidRuntime: java.lang.RuntimeException: Unable to stop activity {org.libreoffice/org.libreoffice.LibreOfficeMainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void org.libreoffice.LOKitTileProvider.cacheDocument()' on a null object reference
E AndroidRuntime:        at android.app.ActivityThread.callActivityOnStop(ActivityThread.java:4624)
E AndroidRuntime:        at android.app.ActivityThread.performStopActivityInner(ActivityThread.java:4594)
E AndroidRuntime:        at android.app.ActivityThread.handleStopActivity(ActivityThread.java:4669)
E AndroidRuntime:        at android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:233)
E AndroidRuntime:        at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:201)
E AndroidRuntime:        at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:173)
E AndroidRuntime:        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97)
E AndroidRuntime:        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
E AndroidRuntime:        at android.os.Handler.dispatchMessage(Handler.java:107)
E AndroidRuntime:        at android.os.Looper.loop(Looper.java:214)
E AndroidRuntime:        at android.app.ActivityThread.main(ActivityThread.java:7356)
E AndroidRuntime:        at java.lang.reflect.Method.invoke(Native Method)
E AndroidRuntime:        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
E AndroidRuntime:        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
E AndroidRuntime: Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void org.libreoffice.LOKitTileProvider.cacheDocument()' on a null object reference
E AndroidRuntime:        at org.libreoffice.LibreOfficeMainActivity.onStop(LibreOfficeMainActivity.java:427)
E AndroidRuntime:        at android.app.Instrumentation.callActivityOnStop(Instrumentation.java:1466)
E AndroidRuntime:        at android.app.Activity.performStop(Activity.java:8018)
E AndroidRuntime:        at android.app.ActivityThread.callActivityOnStop(ActivityThread.java:4616)
E AndroidRuntime:        ... 13 more

Change-Id: I9f8a9329801b721dbfbc0a49c150f88ec341059c
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/90088
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

1 files changed, 2 insertions, 1 deletions

diff --git a/android/source/src/java/org/libreoffice/LibreOfficeMainActivity.java b/android/source/src/java/org/libreoffice/LibreOfficeMainActivity.java
index 628305d01f13..cbc628e94e48 100644
--- a/android/source/src/java/org/libreoffice/LibreOfficeMainActivity.java
+++ b/android/source/src/java/org/libreoffice/LibreOfficeMainActivity.java
@@ -424,7 +424,8 @@ public class LibreOfficeMainActivity extends AppCompatActivity implements Settin
     protected void onStop() {
         Log.i(LOGTAG, "onStop..");
         //save document to cache
-        mTileProvider.cacheDocument();
+        if (mTileProvider != null)
+            mTileProvider.cacheDocument();
         hideSoftKeyboardDirect();
         LOKitShell.sendCloseEvent();
         super.onStop();