Charts: Avoid crash if database fetch fails

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/activities/charts/AbstractChartFragment.java

@@ -368,12 +368,18 @@ public abstract class AbstractChartFragment<D extends ChartsData> extends Abstra
         protected void onPostExecute(final Object o) {
             super.onPostExecute(o);
             final FragmentActivity activity = getActivity();
-            if (activity != null && !activity.isFinishing() && !activity.isDestroyed()) {
-                updateChartsnUIThread(chartsData);
-                renderCharts();
-            } else {
+            if (activity == null || activity.isFinishing() || activity.isDestroyed()) {
                 LOG.info("Not rendering charts because activity is not available anymore");
+                return;
             }
+            if (getTaskError() != null) {
+                // Async task failed - we will have no data, so avoid NPE crashes
+                // a log + toast were already displayed by the DBAccess class
+                return;
+            }
+
+            updateChartsnUIThread(chartsData);
+            renderCharts();
         }
     }
 

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/database/DBAccess.java

@@ -20,6 +20,8 @@ import android.content.Context;
 import android.os.AsyncTask;
 import android.widget.Toast;
 
+import androidx.annotation.Nullable;
+
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -63,7 +65,10 @@ public abstract class DBAccess extends AsyncTask {
         }
     }
 
-
+    @Nullable
+    public Exception getTaskError() {
+        return mError;
+    }
 
     protected void displayError(Throwable error) {
         GB.toast(getContext(), getContext().getString(R.string.dbaccess_error_executing, error.getMessage()), Toast.LENGTH_LONG, GB.ERROR, error);