segmentation fault with method "MCMC+BAS" if initial (best model) arg is not the null model

[merliseclyde]

Describe the bug
bas.lm using method = "MCMC+BAS" crashes with a segmentation fault if bestmodel is not NULL or the null model.

To Reproduce
Steps to reproduce the behavior:

data(Hald) bas.lm(Y ~ ., prior = "BIC", method = "MCMC+BAS", MCMC.iterations = 1000, n.models=2^4, bestmodel=best, update=8, modelprior = uniform(), data = Hald)

Expected behavior
should exit cleanly. If MCMC.iterations = 0, should give the same result as when method = "BAS"

Screenshots
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Desktop (please complete the following information):

• OS: [OSX Bug Sur]
• R Version [e.g. 4.2.2]

Additional context
Add any other context about the problem here.

[merliseclyde]

Added unit tests; problem resolved after correcting index issue related to the current model position versus the number of Unique models