`getParam` gives incorrect error msg if applied to non-existent node

[paciorek]

code= nimbleCode({
    y[2] ~ dnorm(0,1)
})
m <- nimbleModel(code)
getParam(m,'y[1]','mean')

Error in getParam(m, "y[1]", "mean") : 
  getParam only works for one node at a time, but y[1] includes multiple nodes.