add empty view to viewkeycertsfragment

OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/ViewKeyCertsFragment.java

@@ -124,6 +124,8 @@ public class ViewKeyCertsFragment extends Fragment
         } catch (ApiLevelTooLowException e) {
         }
 
+        mStickyList.setEmptyView(getActivity().findViewById(R.id.empty));
+
         // TODO this view is made visible if no data is available
         // mStickyList.setEmptyView(getActivity().findViewById(R.id.empty));
 

OpenPGP-Keychain/src/main/res/layout/view_key_certs_fragment.xml

@@ -33,6 +33,16 @@
             android:layout_alignParentRight="true"
             android:layout_marginRight="16dp" />
 
+        <TextView
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:textAppearance="?android:attr/textAppearanceMedium"
+            android:text="@string/empty_certs"
+            android:id="@+id/empty"
+            android:visibility="gone"
+            android:layout_centerInParent="true"
+            android:paddingBottom="32dp" />
+
     </RelativeLayout>
 
 </ScrollView>

OpenPGP-Keychain/src/main/res/values/strings.xml

@@ -452,5 +452,6 @@
     <string name="label_user_id">User ID</string>
     <string name="label_subkey_rank">Subkey Rank</string>
     <string name="unknown_uid"><![CDATA[<unknown>]]></string>
+    <string name="empty_certs">No certificates for this key</string>
 
 </resources>