Truncate annotation page label instead of error

Truncates annotationPageLabel to be at most maxAnnotationPageLabelLength so the error is not thrown if annotation page label is too long.
Fixes: zotero#131

model/Items.inc.php

@@ -1849,12 +1849,15 @@ public static function updateFromJSON(Zotero_Item $item,
 				case 'annotationText':
 				case 'annotationComment':
 				case 'annotationColor':
-				case 'annotationPageLabel':
 				case 'annotationSortIndex':
 				case 'annotationPosition':
 					$item->$key = $val;
 					break;
-
+
+				case 'annotationPageLabel':
+					$item->$key = substr($val, 0, Zotero_Items::$maxAnnotationPageLabelLength);
+					break;
+
 				case 'dateModified':
 					if ($apiVersion >= 3 && $tmpZoteroClientDateModifiedHack) {
 						$item->setField($key, $val);