BUG: set the default value of the idx and idy to solve the bug 863

Applications/Projections/otbConvertSensorToGeoPoint.cxx

@@ -67,8 +67,10 @@ private:
     AddParameter(ParameterType_Group, "input", "Point Coordinates");
     AddParameter(ParameterType_Float, "input.idx","X value of desired point");
     SetParameterDescription("input.idx", "X coordinate of the point to transform.");
+    SetDefaultParameterFloat("input.idx",0.0);
     AddParameter(ParameterType_Float, "input.idy","Y value of desired point");
     SetParameterDescription("input.idy", "Y coordinate of the point to transform.");
+    SetDefaultParameterFloat("input.idy",0.0); 
 
     // Output with Output Role
     AddParameter(ParameterType_Group, "output", "Geographic Coordinates");