Add default value for remote_id

Fixes SQLite migration with non-null column.

apps/files_sharing/appinfo/database.xml

@@ -25,6 +25,7 @@
 			<field>
 				<name>remote_id</name>
 				<type>integer</type>
+				<default>-1</default>
 				<notnull>true</notnull>
 				<length>4</length>
 			</field>