[Bug]: PCA module fails when trying to add a new card

### What happened?

```r
[WARN] 2025-10-21 15:23:48.1568 pid:10420 token:[46fd689f] te[WARN] 2025-10-21 15:23:48.1568 pid:10420 token:[46fd689f] teal.modules.hermes 'experiments' dropped; see 'drops()'
al.modules.hermes 'experiments' dropped; see 'drops()'
Warning: Error in as.character.default: no method for coercing this S4 class to a vector
95: as.character.default
93: paste
92: commonmark::markdown_html
90: .toHTML.default [C:/Rprojects/teal.reporter/R/toHTML.R#122]
87: toHTML.default [C:/Rprojects/teal.reporter/R/toHTML.R#111]
85: lapply
84: reporter$append_cards [C:/Rprojects/teal.reporter/R/Reporter.R#63]
83: observe [C:/Rprojects/teal.reporter/R/add_card.R#195]
82:
3: runApp
2: print.shiny.appobj
1:
```

### Relevant log output

_No response_

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