Fixed multi-detector bug in gtCalculateGrain

Signed-off-by: Nicola Vigano <nicola.vigano@esrf.fr>

4_grains/gtCalculateGrain_p.m

@@ -142,12 +142,13 @@ for det_ind = app.det_ind
             'Acquisition type should be: {"dct"} | "topotomo", but "%s" was given ("360degree" corresponds to "dct")', ...
             mode);
     end
-
-    if (is_topotomo)
-        if (isempty(app.pl_ind))
+    if (is_topotomo && isempty(app.pl_ind))
+        if (~isfield(acq, 'pl_ind') || isempty(acq.pl_ind))
             warning('gtCalculateGrain:wrong_argument', ...
                 'When mode is "topotomo", "pl_ind" should also be pased');
-            continue;
+            continue
+        else
+            app.pl_ind = acq.pl_ind;
         end
     end