diff -r b1144bb36605 -r c70aefcadf66 PLCControler.py
--- a/PLCControler.py	Tue Apr 22 10:25:24 2008 +0200
+++ b/PLCControler.py	Tue Apr 22 16:16:00 2008 +0200
@@ -1797,6 +1797,8 @@
         element = self.GetEditedElement(tagname)
         if element is not None:
             block = element.getinstance(id)
+            if block is None:
+                return 
             old_name = block.getinstanceName()
             old_type = block.gettypeName()
             new_name = infos.get("name", old_name)
@@ -1871,6 +1873,8 @@
         element = self.GetEditedElement(tagname)
         if element is not None:
             variable = element.getinstance(id)
+            if variable is None:
+                return 
             for param, value in infos.items():
                 if param == "name":
                     variable.setexpression(value)    
@@ -1935,6 +1939,8 @@
         element = self.GetEditedElement(tagname)
         if element is not None:
             connection = element.getinstance(id)
+            if connection is None:
+                return
             for param, value in infos.items():
                 if param == "name":
                     connection.setname(value)    
@@ -1995,6 +2001,8 @@
         element = self.GetEditedElement(tagname)
         if element is not None:
             powerrail = element.getinstance(id)
+            if powerrail is None:
+                return
             for param, value in infos.items():
                 if param == "height":
                     powerrail.setheight(value)
@@ -2032,6 +2040,8 @@
         element = self.GetEditedElement(tagname)
         if element is not None:
             contact = element.getinstance(id)
+            if contact is None:
+                return
             for param, value in infos.items():
                 if param == "name":
                     contact.setvariable(value)
@@ -2078,6 +2088,8 @@
         element = self.GetEditedElement(tagname)
         if element is not None:
             coil = element.getinstance(id)
+            if coil is None:
+                return
             for param, value in infos.items():
                 if param == "name":
                     coil.setvariable(value)
@@ -2124,6 +2136,8 @@
         element = self.GetEditedElement(tagname)
         if element is not None:
             step = element.getinstance(id)
+            if step is None:
+                return
             for param, value in infos.items():
                 if param == "name":
                     step.setname(value)
@@ -2172,6 +2186,8 @@
         element = self.GetEditedElement(tagname)
         if element is not None:
             transition = element.getinstance(id)
+            if transition is None:
+                return
             for param, value in infos.items():
                 if param == "type" and value != "connection":
                     transition.setconditionContent(value, infos["condition"])
@@ -2225,6 +2241,8 @@
         element = self.GetEditedElement(tagname)
         if element is not None:
             divergence = element.getinstance(id)
+            if divergence is None:
+                return
             for param, value in infos.items():
                 if param == "height":
                     divergence.setheight(value)
@@ -2279,6 +2297,8 @@
         element = self.GetEditedElement(tagname)
         if element is not None:
             jump = element.getinstance(id)
+            if jump is None:
+                return
             for param, value in infos.items():
                 if param == "target":
                     jump.settargetName(value)
@@ -2307,6 +2327,8 @@
         element = self.GetEditedElement(tagname)
         if element is not None:
             actionBlock = element.getinstance(id)
+            if actionBlock is None:
+                return
             for param, value in infos.items():
                 if param == "actions":
                     actionBlock.setactions(value)