Fix detection of invalid textObject in getTextFromObject()

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Author: TobiGr

extractor/src/main/java/org/schabi/newpipe/extractor/services/youtube/linkHandler/YoutubeParsingHelper.java

@@ -391,6 +391,10 @@ public static String getUrlFromNavigationEndpoint(JsonObject navigationEndpoint)
      * @return text in the JSON object or an empty string
      */
     public static String getTextFromObject(JsonObject textObject, boolean html) throws ParsingException {
+        if (textObject == null || textObject.isEmpty()) {
+            return null;
+        }
+
         if (textObject.has("simpleText")) return textObject.getString("simpleText");
 
         StringBuilder textBuilder = new StringBuilder();