Don't use CharSequence as notification text

If a notification changes the color etc. on the CharSequence, then
it overrode our colors. Gmail for instance always makes the second
text dark (apparently), overriding our dark theme.

Change-Id: Ibd8751d70849fd10fd0114af02d382aba1771d4e
diff --git a/src/com/android/launcher3/notification/NotificationMainView.java b/src/com/android/launcher3/notification/NotificationMainView.java
index 0d6da77..9b8dd64 100644
--- a/src/com/android/launcher3/notification/NotificationMainView.java
+++ b/src/com/android/launcher3/notification/NotificationMainView.java
@@ -87,11 +87,11 @@
         CharSequence title = mNotificationInfo.title;
         CharSequence text = mNotificationInfo.text;
         if (!TextUtils.isEmpty(title) && !TextUtils.isEmpty(text)) {
-            mTitleView.setText(title);
-            mTextView.setText(text);
+            mTitleView.setText(title.toString());
+            mTextView.setText(text.toString());
         } else {
             mTitleView.setMaxLines(2);
-            mTitleView.setText(TextUtils.isEmpty(title) ? text : title);
+            mTitleView.setText(TextUtils.isEmpty(title) ? text.toString() : title.toString());
             mTextView.setVisibility(GONE);
         }
         iconView.setBackground(mNotificationInfo.getIconForBackground(getContext(),