Do not load silx fbp algorithm is pyopencl of the fbp not here

tomogui/gui/datasource/QDataSourceWidget.py

@@ -42,6 +42,12 @@ try:
 except ImportError:
     from tomogui.third_party.configuration import config as freeartconfig
     found_freeart = False
+try:
+    import pyopencl
+    from silx.opencl.backprojection import Backprojection
+    found_fbp = True
+except ImportError:
+    found_fbp = False
 
 _logger = logging.getLogger(__file__)
 
@@ -150,25 +156,32 @@ class QDataSourceWidget(qt.QWidget, ConfigurationActor):
         cb = qt.QComboBox(parent)
         # Warning : should always be stored in this order, otherwise may fail
         # Would be better to link it from the FreeARTReconsParam...
-        cb.addItem(QDataSourceWidget.SILX_FBP_DEF)
-        cb.setItemData(0,
-                       QDataSourceWidget._getSilxFBPReconsInfo(),
-                       qt.Qt.ToolTipRole)
+        iItem = 0
+        if found_fbp is True:
+            cb.addItem(QDataSourceWidget.SILX_FBP_DEF)
+            cb.setItemData(iItem,
+                           QDataSourceWidget._getSilxFBPReconsInfo(),
+                           qt.Qt.ToolTipRole)
+            iItem += 1
         if found_freeart is True:
             cb.addItem(QDataSourceWidget.FREEART_TX_DEF)
-            cb.setItemData(1,
+            cb.setItemData(iItem,
                            QDataSourceWidget._getTransmissionReconsInfo(),
                            qt.Qt.ToolTipRole)
+            iItem += 1
 
             cb.addItem(QDataSourceWidget.FREEART_COMPTON_DEF)
-            cb.setItemData(2,
+            cb.setItemData(iItem,
                            QDataSourceWidget._getComptonReconsInfo(),
                            qt.Qt.ToolTipRole)
+            iItem += 1
 
             cb.addItem(QDataSourceWidget.FREEART_FLUO_DEF)
-            cb.setItemData(3,
+            cb.setItemData(iItem,
                            QDataSourceWidget._getFluoReconsInfo(),
                            qt.Qt.ToolTipRole)
+            iItem += 1
+
         return cb
 
     def getShortToolTip(self):