ASSERTION ERROR: Stored value should never be NO_CHANGE code example

Example: ERROR Error: ASSERTION ERROR: Stored value should never be NO_CHANGE.

This error message happens when a pipe executes badly and
returns no value.

By default pipes are "pure" which means that the function is not
called on every change detection cycle.If the pipe's input value does
not change, angular use the last returned value which does not exist
and you have a "Stored value should never be NO_CHANGE" message in 
the console.