Fix Crash Edit Categories Fragment (commons-app#5510)

* fix crash

* Tests Added

* Tests and Null Checks Added

Author: shashankiitbhu

app/src/main/java/fr/free/nrw/commons/upload/categories/UploadCategoriesFragment.java

@@ -102,17 +102,17 @@ public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceStat
             wikiText = bundle.getString("WikiText");
             nearbyPlaceCategory = bundle.getString(SELECTED_NEARBY_PLACE_CATEGORY);
         }
-        if(callback!=null) {
-            init();
-            presenter.getCategories().observe(getViewLifecycleOwner(), this::setCategories);
-        }
+        init();
+        presenter.getCategories().observe(getViewLifecycleOwner(), this::setCategories);
 
     }
 
     private void init() {
         if (media == null) {
-            tvTitle.setText(getString(R.string.step_count, callback.getIndexInViewFlipper(this) + 1,
-                callback.getTotalNumberOfSteps(), getString(R.string.categories_activity_title)));
+            if (callback != null) {
+                tvTitle.setText(getString(R.string.step_count, callback.getIndexInViewFlipper(this) + 1,
+                    callback.getTotalNumberOfSteps(), getString(R.string.categories_activity_title)));
+            }
         } else {
             tvTitle.setText(R.string.edit_categories);
             tvSubTitle.setVisibility(View.GONE);
@@ -221,7 +221,9 @@ public void run() {
 
     @Override
     public void goToNextScreen() {
-        callback.onNextButtonClicked(callback.getIndexInViewFlipper(this));
+        if (callback != null){
+            callback.onNextButtonClicked(callback.getIndexInViewFlipper(this));
+        }
     }
 
     @Override
@@ -314,7 +316,9 @@ public void onPreviousButtonClicked() {
             mediaDetailFragment.onResume();
             goBackToPreviousScreen();
         } else {
-            callback.onPreviousButtonClicked(callback.getIndexInViewFlipper(this));
+            if (callback != null) {
+                callback.onPreviousButtonClicked(callback.getIndexInViewFlipper(this));
+            }
         }
     }
 

app/src/test/kotlin/fr/free/nrw/commons/upload/categories/UploadCategoriesFragmentUnitTests.kt

@@ -4,6 +4,7 @@ import android.app.ProgressDialog
 import android.content.Context
 import android.os.Looper
 import android.text.Editable
+import android.util.Log
 import android.view.LayoutInflater
 import android.view.View
 import android.widget.Button
@@ -116,7 +117,6 @@ class UploadCategoriesFragmentUnitTests {
         Whitebox.setInternalState(fragment, "pbCategories", pbCategories)
         Whitebox.setInternalState(fragment, "tilContainerEtSearch", tilContainerEtSearch)
         Whitebox.setInternalState(fragment, "adapter", adapter)
-        Whitebox.setInternalState(fragment, "callback", callback)
         Whitebox.setInternalState(fragment, "presenter", presenter)
         Whitebox.setInternalState(fragment, "etSearch", etSearch)
         Whitebox.setInternalState(fragment, "rvCategories", rvCategories)
@@ -365,4 +365,15 @@ class UploadCategoriesFragmentUnitTests {
         method.invoke(fragment)
     }
 
-}
+    @Test
+    @Throws(Exception::class)
+    fun `Test init when callback is null`() {
+        Shadows.shadowOf(Looper.getMainLooper()).idle()
+        val method: Method = UploadCategoriesFragment::class.java.getDeclaredMethod(
+            "init"
+        )
+        method.isAccessible = true
+        method.invoke(fragment)
+    }
+
+}