[YouTube] Fix NPE in search when getting channel items without subscriber count

extractor/src/main/java/org/schabi/newpipe/extractor/services/youtube/extractors/YoutubeChannelInfoItemExtractor.java

@@ -96,8 +96,12 @@ public class YoutubeChannelInfoItemExtractor implements ChannelInfoItemExtractor
             }
 
             if (withHandle) {
-                return Utils.mixedNumberWordToLong(getTextFromObject(
-                        channelInfoItem.getObject("videoCountText")));
+                if (channelInfoItem.has("videoCountText")) {
+                    return Utils.mixedNumberWordToLong(getTextFromObject(
+                            channelInfoItem.getObject("videoCountText")));
+                } else {
+                    return -1;
+                }
             }
 
             return Utils.mixedNumberWordToLong(getTextFromObject(