binary_search fix

[pm100]

simple fix for #449

if we were down to a slice with size == 1 then code tried to access slice[1]

[stale]

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[faheel]

The following seems like a simpler fix as it prevents the function call for the second time if the value was not found, and also does not require checking the size in each recursive call:

- else if (low <= high)
+ else if (low < high)

[pm100]

quite right :-)