The isExported option should only apply to files

tests/reference/proj/1_nwProject.nwx

@@ -1,5 +1,5 @@
 <?xml version='1.0' encoding='utf-8'?>
-<novelWriterXML appVersion="0.5" fileVersion="1.0" saveCount="1" autoCount="0" timeStamp="2020-05-10 19:32:32">
+<novelWriterXML appVersion="0.5" fileVersion="1.0" saveCount="1" autoCount="0" timeStamp="2020-05-10 23:16:14">
   <project>
     <name></name>
     <title></title>
@@ -42,7 +42,6 @@
       <class>NOVEL</class>
       <status>New</status>
       <expanded>False</expanded>
-      <exported>True</exported>
     </item>
     <item handle="44cb730c42048" order="None" parent="None">
       <name>Characters</name>
@@ -50,7 +49,6 @@
       <class>CHARACTER</class>
       <status>New</status>
       <expanded>False</expanded>
-      <exported>True</exported>
     </item>
     <item handle="71ee45a3c0db9" order="None" parent="None">
       <name>Plot</name>
@@ -58,7 +56,6 @@
       <class>PLOT</class>
       <status>New</status>
       <expanded>False</expanded>
-      <exported>True</exported>
     </item>
     <item handle="811786ad1ae74" order="None" parent="None">
       <name>World</name>
@@ -66,7 +63,6 @@
       <class>WORLD</class>
       <status>New</status>
       <expanded>False</expanded>
-      <exported>True</exported>
     </item>
     <item handle="25fc0e7096fc6" order="None" parent="73475cb40a568">
       <name>New Chapter</name>
@@ -74,7 +70,6 @@
       <class>NOVEL</class>
       <status>New</status>
       <expanded>False</expanded>
-      <exported>True</exported>
     </item>
     <item handle="31489056e0916" order="None" parent="25fc0e7096fc6">
       <name>New Scene</name>