Error bar on data buggy

[swertz]

There's a strange issue with the error bar on data when only one entry is in the bin:

On the other hand on other plots (produced at the same time as above) it seems fine:

Weird, right?

[blinkseb]

That's indeed really strange. What happen if you try to draw only the first plot (the buggy one)?

[swertz]

Same result... It's just crazy that the bin with two entries has the error going lower!

[swertz]

So: understood why these plots were buggy (HLT scale factors should be = 1 on data, duh), but not why ROOT plots the error bars like that (bin has entry = 0.966).