CI: enable testing via Github Actions.

.github/workflows/test.yml

@@ -0,0 +1,21 @@
+#https://github.com/marketplace/actions/android-emulator-runner
+name: Test
+on: [push, pull_request]
+jobs:
+  test:
+    runs-on: macos-latest
+    strategy:
+      matrix:
+        api-level: [21, 29]
+        target: [default]
+    steps:
+      - name: checkout
+        uses: actions/checkout@v2
+
+      - name: run tests
+        uses: reactivecircus/android-emulator-runner@v2
+        with:
+          api-level: ${{ matrix.api-level }}
+          target: ${{ matrix.target }}
+          arch: x86_64
+          script: ./gradlew connectedCheck

src/main/java/de/dennisguse/opentracks/content/provider/ContentProviderUtils.java

@@ -187,7 +187,7 @@ public class ContentProviderUtils {
         contentResolver.delete(TracksColumns.CONTENT_URI, null, null);
 
         File dir = FileUtils.getPhotoDir(context);
-        deleteDirectoryRecurse(context, dir);
+        deleteDirectoryRecurse(dir);
     }
 
     /**
@@ -216,7 +216,7 @@ public class ContentProviderUtils {
 
         contentResolver.delete(WaypointsColumns.CONTENT_URI, WaypointsColumns.TRACKID + "=?",
                 new String[]{Long.toString(trackId)});
-        deleteDirectoryRecurse(context, FileUtils.getPhotoDir(context, trackId));
+        deleteDirectoryRecurse(FileUtils.getPhotoDir(context, trackId));
     }
 
     /**
@@ -224,10 +224,10 @@ public class ContentProviderUtils {
      *
      * @param dir the directory
      */
-    private void deleteDirectoryRecurse(Context context, File dir) {
+    private void deleteDirectoryRecurse(File dir) {
-        if (dir.exists() && dir.isDirectory()) {
+        if (dir != null && dir.exists() && dir.isDirectory()) {
             for (File child : dir.listFiles()) {
-                deleteDirectoryRecurse(context, child);
+                deleteDirectoryRecurse(child);
             }
             dir.delete();
         }