chart_Series theme is disturbed by add_TA

### Description

Cannot hide vertical axis through custom _theme_ when _add_TA_ is present in _chart_Series._

### Expected behavior

_add_TA_ should not interfere with the selected theme. _add_BBands_, for example, behaves correctly.

### Minimal, reproducible example

```r
getSymbols('T', from='2017-06-06')
myTheme <- chart_theme()
myTheme$rylab <- FALSE # hide right y-axis
chart_Series(T, theme=myTheme) # works ok
chart_Series(T, theme=myTheme, TA='add_TA(EMA(Cl(T)), on=1)') # does not hide axis
```

Reproduce the issue with chart_Series(T, theme=myTheme, TA='add_TA(EMA(Cl(T)), on=1)') using the example, then compare it with the working add_BBands case. Trace chart_Series and add_TA to find where the custom theme is overridden. Done means the custom theme hides the right y-axis even when add_TA is present.

Written by the indexing model from the issue text.