Fix trying to launch a dialog from an application context

res/values/strings.xml

@@ -1311,6 +1311,8 @@
     <string name="transport_selection_list_item__transport_icon">Transport icon</string>
     <string name="ConversationListFragment_loading">Loading...</string>
     <string name="CallNotificationBuilder_connecting">Connecting...</string>
+    <string name="Permissions_permission_required">Permission required</string>
+    <string name="Permissions_continue">Continue</string>
 
 
     <!-- EOF -->

src/org/thoughtcrime/securesms/permissions/Permissions.java

@@ -22,9 +22,11 @@ import android.view.WindowManager;
 import com.annimon.stream.Stream;
 import com.annimon.stream.function.Consumer;
 
+import org.thoughtcrime.securesms.R;
 import org.thoughtcrime.securesms.util.LRUCache;
 import org.thoughtcrime.securesms.util.ServiceUtil;
 
+import java.lang.ref.WeakReference;
 import java.security.SecureRandom;
 import java.util.List;
 import java.util.Map;
@@ -309,22 +311,26 @@ public class Permissions {
 
   private static class SettingsDialogListener implements Runnable {
 
-    private final Context context;
+    private final WeakReference<Context> context;
     private final String                 message;
 
     SettingsDialogListener(Context context, String message) {
       this.message = message;
-      this.context = context.getApplicationContext();
+      this.context = new WeakReference<>(context);
     }
 
     @Override
     public void run() {
+      Context context = this.context.get();
+
+      if (context != null) {
         new AlertDialog.Builder(context)
-          .setTitle("Permission required")
+            .setTitle(R.string.Permissions_permission_required)
             .setMessage(message)
-          .setPositiveButton("Continue", (dialog, which) -> context.startActivity(getApplicationSettingsIntent(context)))
+            .setPositiveButton(R.string.Permissions_continue, (dialog, which) -> context.startActivity(getApplicationSettingsIntent(context)))
-          .setNegativeButton("Cancel", null)
+            .setNegativeButton(android.R.string.cancel, null)
             .show();
       }
     }
   }
+}