Index: /trunk/src/sub_field.m
===================================================================
--- /trunk/src/sub_field.m	(revision 164)
+++ /trunk/src/sub_field.m	(revision 165)
@@ -348,10 +348,12 @@
     DimCell=[DimCell Field_1.VarDimName([VarType_1.vector_x VarType_1.vector_y ])];
     SubData.VarDimName=[SubData.VarDimName DimCell];
-    if ~(isfield(SubData,'VarAttribute') && numel(SubData.VarAttribute)==numel(SubData.ListVarName))
-        for ivar=numel(SubData.VarAttribute)+1:numel(SubData.ListVarName)-4
-             SubData.VarAttribute{ivar}=[];
-        end
-    end
-    SubData.VarAttribute=[SubData.VarAttribute {XAttr} {YAttr} {UAttr} {VAttr}];
+    if isfield(SubData,'VarAttribute')
+        if ~(numel(SubData.VarAttribute)==numel(SubData.ListVarName))
+            for ivar=numel(SubData.VarAttribute)+1:numel(SubData.ListVarName)-4
+                SubData.VarAttribute{ivar}=[];
+            end
+        end
+        SubData.VarAttribute=[SubData.VarAttribute {XAttr} {YAttr} {UAttr} {VAttr}];
+    end
     eval(['SubData.' XName_1_1 '=Field_1.' XName_1 ';'])
     eval(['SubData.' YName_1_1 '=Field_1.' YName_1 ';'])