environment with candleChart

The call to `f` works but there is some inconsistency somewhere as one needs `print(...)` for `addRSI` and `addBBands` (or else they do not appear) but not `addLines`. `print(addLines(...))` works so this is not really a bug but it seemed strange.

Also, the `zoomChart(...)` fails with an error message about not being able to find `at`. (If `at` is placed in the global environment then it works.)
````
library(quantmod)
if (!exists("IBM")) getSymbols("IBM")

f <- function() {
at <- c(10, 500)
candleChart(IBM, theme = chartTheme("white"))
print(addRSI())
print(addBBands())
addLines(v = at)
}
f()
zoomChart("last 3 months")
````

Start by running the supplied R example with quantmod, focusing on candleChart(), addRSI(), addBBands(), addLines(), and zoomChart(). Trace why some chart additions require print() and why zoomChart("last 3 months") cannot find the local at value; done means the example behaves consistently without relying on a global at.

Written by the indexing model from the issue text.