Improve error message for elements not available in the formula

[auzaheta]

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When model specification includes actors' attributes that don't exist in the nodes' data frame, the error is not informative.

library(goldfish)
data("Social_Evolution")
callNetwork <- defineNetwork(nodes = actors, directed = TRUE)
callNetwork <- linkEvents(x = callNetwork, changeEvent = calls, nodes = actors)
callsDependent <- defineDependentEvents(events = calls, nodes = actors, defaultNetwork = callNetwork)

mod <- estimate(callsDependent ~ inertia + alter(actors$uno))
> Error in getElementFromDataObjectTable(objectNameTable, envir = envir)[[1]] : 
> subscript out of bounds

Describe the solution you'd like
An informative error indicating that the formula uses objects not available.