[TomoScanBase] add the possibility to get only one return projection

tomoscan/scanbase.py

@@ -326,6 +326,8 @@ class TomoScanBase:
                 else:
                     res['90(1)'] = ordered_url[extraImgs[0]]
                     res['0(1)'] = ordered_url[extraImgs[1]]
+            elif len(extraImgs) == 1:
+                    res['0(1)'] = ordered_url[extraImgs[0]]
             else:
                 raise ValueError('incoherent data information to retrieve scan'
                                  'extra images angle')