Fixing NXcrystal_structure

Author: atomprobe-tc

base_classes/NXcrystal_structure.nxdl.xml

@@ -54,7 +54,7 @@
              to resolve ambiguity when the reference frame is different
              to the NeXus default reference frame (McStas).
         </doc>
-    </attribute>
+    </field>
     <field name="dimensionality" type="NX_POSINT">
         <doc>
              Dimensionality of the structure.