[Fix #3763] Do not call cider-docstring fns unless we have a doc (#3764)

Sometimes, there is no "doc" attribute in the nrepl-dict. In such
cases, `fetched-doc` is nil, which causes `cider-docstring--*`
functions to error.

We should only call these functions when we have a docstring to
render.

Author: vedang

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## master (unreleased)
 
+### Bugs fixed
+
+- [#3763](https://github.com/clojure-emacs/cider/issues/3763): Fix `cider-docview-render` completion popup error when symbol being completed does not have a docstring.
+
 ## 1.16.1 (2024-12-03)
 
 ### Changes

cider-doc.el

@@ -428,10 +428,11 @@ in a COMPACT format is specified, FOR-TOOLTIP if specified."
                                                             "doc-first-sentence-fragments" (nrepl-dict-get info "doc-first-sentence-fragments"))))
          (fetched-doc (nrepl-dict-get info "doc"))
          (doc     (or rendered-fragments
-                      (if compact
-                          (cider-docstring--trim
-                           (cider-docstring--format fetched-doc))
-                        fetched-doc)
+                      (when fetched-doc
+                        (if compact
+                            (cider-docstring--trim
+                             (cider-docstring--format fetched-doc))
+                          fetched-doc))
                       (unless compact
                         "Not documented.")))
          (url     (nrepl-dict-get info "url"))