Failed to create timseries in ACLED

[cdbethune]

Creating a timeseries from the ACLED dataset using event data, fatalities and country as the series ID leads fails and generates the following server output:

2021/02/10 16:20:32 http: panic serving [::1]:51172: runtime error: index out of range [-1]
goroutine 178 [running]:
net/http.(*conn).serve.func1(0xc00014c1e0)
        /usr/lib/go/src/net/http/server.go:1801 +0x147
panic(0x10e9780, 0xc0004d2000)
        /usr/lib/go/src/runtime/panic.go:975 +0x47a
github.com/uncharted-distil/distil/api/task.CreateComposedVariable(0x12fa060, 0xc001190e70, 0x12fc880, 0xc001190e40, 0xc001088046, 0xb, 0xc000594c50, 0xd, 0xc0006bbc20, 0x12, ...)
        /home/chris/dev/git_work/distil/api/task/prediction.go:577 +0x905
github.com/uncharted-distil/distil/api/routes.createGrouping(0xc001088046, 0xb, 0xc000594c50, 0xd, 0xc000cf0780, 0xa, 0xc001190de0, 0x12fa060, 0xc001190e70, 0x12fc880, ...)
        /home/chris/dev/git_work/distil/api/routes/grouping.go:219 +0x5dd
github.com/uncharted-distil/distil/api/routes.GroupingHandler.func1(0x12e34e0, 0xc0003832a0, 0xc0004ca600)
        /home/chris/dev/git_work/distil/api/routes/grouping.go:69 +0x2b4
net/http.HandlerFunc.ServeHTTP(0xc00000e9e0, 0x12e34e0, 0xc0003832a0, 0xc0004ca600)
        /usr/lib/go/src/net/http/server.go:2042 +0x44
goji.io/v3.dispatch.ServeHTTP(0x12e34e0, 0xc0003832a0, 0xc0004ca600)
        /home/chris/dev/go_workspace/pkg/mod/goji.io/[email protected]/dispatch.go:17 +0xba
github.com/uncharted-distil/distil/api/middleware.Gzip.func1(0x7f7f043c28e0, 0xc0010aa2c0, 0xc0004ca600)
        /home/chris/dev/git_work/distil/api/middleware/gzip.go:61 +0x282
net/http.HandlerFunc.ServeHTTP(0xc00034a340, 0x7f7f043c28e0, 0xc0010aa2c0, 0xc0004ca600)
        /usr/lib/go/src/net/http/server.go:2042 +0x44
github.com/uncharted-distil/distil/api/middleware.Log.func1(0x12e30e0, 0xc000254ee0, 0xc0004ca600)
        /home/chris/dev/git_work/distil/api/middleware/log_http.go:37 +0x25f
net/http.HandlerFunc.ServeHTTP(0xc00034a360, 0x12e30e0, 0xc000254ee0, 0xc0004ca600)
        /usr/lib/go/src/net/http/server.go:2042 +0x44
goji.io/v3.(*Mux).ServeHTTP(0xc0004d5300, 0x12e30e0, 0xc000254ee0, 0xc0004ca200)
        /home/chris/dev/go_workspace/pkg/mod/goji.io/[email protected]/mux.go:74 +0x1d1
net/http.serverHandler.ServeHTTP(0xc0003cf420, 0x12e30e0, 0xc000254ee0, 0xc0004ca200)
        /usr/lib/go/src/net/http/server.go:2843 +0xa3
net/http.(*conn).serve(0xc00014c1e0, 0x12eb460, 0xc0004a0400)
        /usr/lib/go/src/net/http/server.go:1925 +0x8ad
created by net/http.(*Server).Serve
        /usr/lib/go/src/net/http/server.go:2969 +0x36c
2
2021/02/10 16:20:32 http: panic serving [::1]:51172: runtime error: index out of range [-1]
goroutine 178 [running]:
net/http.(*conn).serve.func1(0xc00014c1e0)
        /usr/lib/go/src/net/http/server.go:1801 +0x147
panic(0x10e9780, 0xc0004d2000)
        /usr/lib/go/src/runtime/panic.go:975 +0x47a
github.com/uncharted-distil/distil/api/task.CreateComposedVariable(0x12fa060, 0xc001190e70, 0x12fc880, 0xc001190e40, 0xc001088046, 0xb, 0xc000594c50, 0xd, 0xc0006bbc20, 0x12, ...)
        /home/chris/dev/git_work/distil/api/task/prediction.go:577 +0x905
github.com/uncharted-distil/distil/api/routes.createGrouping(0xc001088046, 0xb, 0xc000594c50, 0xd, 0xc000cf0780, 0xa, 0xc001190de0, 0x12fa060, 0xc001190e70, 0x12fc880, ...)
        /home/chris/dev/git_work/distil/api/routes/grouping.go:219 +0x5dd
github.com/uncharted-distil/distil/api/routes.GroupingHandler.func1(0x12e34e0, 0xc0003832a0, 0xc0004ca600)
        /home/chris/dev/git_work/distil/api/routes/grouping.go:69 +0x2b4
net/http.HandlerFunc.ServeHTTP(0xc00000e9e0, 0x12e34e0, 0xc0003832a0, 0xc0004ca600)
        /usr/lib/go/src/net/http/server.go:2042 +0x44
goji.io/v3.dispatch.ServeHTTP(0x12e34e0, 0xc0003832a0, 0xc0004ca600)
        /home/chris/dev/go_workspace/pkg/mod/goji.io/[email protected]/dispatch.go:17 +0xba
github.com/uncharted-distil/distil/api/middleware.Gzip.func1(0x7f7f043c28e0, 0xc0010aa2c0, 0xc0004ca600)
        /home/chris/dev/git_work/distil/api/middleware/gzip.go:61 +0x282
net/http.HandlerFunc.ServeHTTP(0xc00034a340, 0x7f7f043c28e0, 0xc0010aa2c0, 0xc0004ca600)
        /usr/lib/go/src/net/http/server.go:2042 +0x44
github.com/uncharted-distil/distil/api/middleware.Log.func1(0x12e30e0, 0xc000254ee0, 0xc0004ca600)
        /home/chris/dev/git_work/distil/api/middleware/log_http.go:37 +0x25f
net/http.HandlerFunc.ServeHTTP(0xc00034a360, 0x12e30e0, 0xc000254ee0, 0xc0004ca600)
        /usr/lib/go/src/net/http/server.go:2042 +0x44
goji.io/v3.(*Mux).ServeHTTP(0xc0004d5300, 0x12e30e0, 0xc000254ee0, 0xc0004ca200)
        /home/chris/dev/go_workspace/pkg/mod/goji.io/[email protected]/mux.go:74 +0x1d1
net/http.serverHandler.ServeHTTP(0xc0003cf420, 0x12e30e0, 0xc000254ee0, 0xc0004ca200)
        /usr/lib/go/src/net/http/server.go:2843 +0xa3
net/http.(*conn).serve(0xc00014c1e0, 0x12eb460, 0xc0004a0400)
        /usr/lib/go/src/net/http/server.go:1925 +0x8ad
created by net/http.(*Server).Serve
        /usr/lib/go/src/net/http/server.go:2969 +0x36c