Checking nil values in the equal function

[gitlw]

fixes #2766

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This change is 

[manishrjain]

Thanks for fixing this quickly. Just ensure you don't cross 100 char limit.

Reviewed 2 of 2 files at r1.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @gitlw and @danielmai)

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types/sort_test.go, line 137 at r1 (raw file):

	// not equal when either parameter has the Value field being nil
	require.False(t, equal(Val{Tid: IntID, Value: int64(3)}, Val{Tid: IntID}), "equal should return false when either parameter cannot have its value converted")

100 char limit per line.