How do we identity NULL Handles?

During the building up of  SystemVerilog Environment sometimes we end in facing NULL Pointer error.

Question is how do we identify the issue ?

Let us look at one small example and analyze.

e.g

                 module test;
                        class       animal;
                               int   age;
                        endclass
                         animal      a_h;      //  class handle pointer
                         initial   begin
                                    a_h.age  =  52;
                                    a_h         = new();
                          end
                      endmodule

****      Here we forgot to call the new() for class animal handle (a_h) 
            before accessing its objects. 
****      Since the Class handle was not created it created NULL Handle issue.
*****    By reversing the handle creation and assignment, we can get ride of 
           NULL pointer issue.
                           

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