Combining `layout=region` and `labels=name` raises errors when combining multiple measures

[sjockers]

Combining layout=region and labels=name does not work when combining multiple measures:

https://tabular.genesapi.org/?parent=08&level=3&data=99910%3AAI0216&data=99910%3AAI0215&format=csv&time=2018&layout=region&labels=name

(may be related to #11)

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Using only labels=name works:

https://tabular.genesapi.org/?parent=08&level=3&data=99910%3AAI0216&data=99910%3AAI0215&format=csv&time=2018&layout=region

Using only layout=region also works:

https://tabular.genesapi.org/?parent=08&level=3&data=99910%3AAI0216&data=99910%3AAI0215&format=csv&time=2018&labels=name