Hello, another day another random problem.

I have just fixed an issue where, I have from someones spreadsheet, two
values.
    A
1:  4
2:  4
3: FORMULA

in forumula =SUM(A3-A4)

If A2 is blank then A3 will come up with #VALUE error, unless I go through
and press DELETE key on the blank Cell in A2.

I didn't create this sheet, but is this #Value appearing before I press
delete, because they've used the SUM function to subtract?

Not a huge issue, just curious because I keep having to fix things coming
from a different department and this #Value issue is bugging me because I
don't know why it does this.

Cheers!