HFArray Bug. Unsure of exact fix.

[swillits]

HFByteArray_FileWriting.m line 439: constructNewSlices() returns HFByteArray, but there's a line returning an NSArray. I've traced the return value far enough to determine there's no special-case handling of constructNewSlices returning an NSArray so it appears this is bug which will cause a crash if ever triggered.

I'm not sure of the correct fix.

static HFByteArray *constructNewSlices(...) {
    ...

    NSUInteger dirtyRangeCount = [dirtyRanges count];
    if (! dirtyRangeCount) return [NSArray arrayWithObject:slice];

[percontation]

The "return NO;" on :458 also scares me (despite it not really breaking anything).