Change message for new users

Fix a bug : updating operations doesn't work

src/view/grid/GridAccount.cpp

@@ -1037,14 +1037,11 @@ void GridAccount::OnOperationModified(int row, int col)
     	{
             need_insertion = true;
             removeRow(row);
-    	    DeleteOperation(cur_op);
-            _displayedOperations.erase(_displayedOperations.begin()+row);
 	    if (fix_cost)
 		_fixCosts--;
-    	}
-        else
-            (_displayedOperations)[row] = new_op;
+	}
 
+	(_displayedOperations)[row] = new_op;
 	UpdateOperation(new_op);
     }
     // Add an operation