l10n: Add a period in the text string

src/main/res/values/strings.xml

@@ -586,7 +586,7 @@
 
     <!-- Activities -->
     <string name="activities_no_results_headline">No activity yet</string>
-    <string name="activities_no_results_message">No events like additions, changes and shares yet</string>
+    <string name="activities_no_results_message">No events like additions, changes and shares yet.</string>
     <string name="prefs_category_about">About</string>
 
     <string name="actionbar_contacts">Back up contacts</string>