#2856 Switch from spectrogram to series leaves "Horizontal Interval Average" which keeps reference to data

[Jeremy Faden]

1. plot vap+inline:n=10000&distance(n,n,n/104,n/104,n/10,n/5)+randn(n,n)/4+outerProduct(sin(linspace(0,10*TAU,n)),ones(n))
2. plot https://www.northwestknowledge.net/metdata/data/bi_2025.nc?burning_index_g, run out of memory error
3. File->Reset
4. plot https://www.northwestknowledge.net/metdata/data/bi_2025.nc?burning_index_g, run out of memory error

I keep running out of memory, and though it's returned to a low-memory series plot a reference to the rank 2 data is kept by "Horizontal Interval Average" mouse module.