style: Consistently use _ for condition-case "don't care" var

As opposed to using variously () or nil.

racket-collection.el

@@ -161,7 +161,7 @@ at the top, marked with \"->\".
 candidates or (point-max)."
   (save-excursion
     (goto-char (point-min))
-    (condition-case ()
+    (condition-case _
         (1- (re-search-forward "\n"))
       (error (point-max)))))
 

racket-common.el

@@ -232,7 +232,7 @@ flavor here."
     ;; Try to move up to outermost form, but stopping at or before any
     ;; module form.
     (while
-        (condition-case nil
+        (condition-case _
             (let ((prev (point)))
               (goto-char (scan-lists (point) -1 1))
               (if (looking-at racket-module-forms)
@@ -249,7 +249,7 @@ flavor here."
     ;; already at the module level, and just need to move to the
     ;; previous module-level item.
     (unless (/= orig (point))
-      (condition-case nil (backward-sexp 1) (scan-error nil)))
+      (condition-case _ (backward-sexp 1) (scan-error nil)))
     ;; When we moved, also move before any preceding "#;".
     (when (/= orig (point))
       (when-let (sexp-comment-start
@@ -318,7 +318,7 @@ Ignores module forms nested (at any depth) in any sort of plain
 or syntax quoting, because those won't be valid Racket syntax."
   (save-excursion
     (let ((xs nil))
-      (condition-case ()
+      (condition-case _
           (progn
             (racket--escape-string-or-comment)
             (while t

racket-complete.el

@@ -12,7 +12,7 @@
 
 (defun racket--call-with-completion-prefix-positions (proc)
   (if forward-sexp-function ;not necessarily sexp lang
-      (condition-case nil
+      (condition-case _
           (save-excursion
             (let ((beg (progn (forward-sexp -1) (point)))
                   (end (progn (forward-sexp  1) (point))))
@@ -22,7 +22,7 @@
   (let ((beg (save-excursion (skip-syntax-backward "^-()>") (point))))
     (unless (or (eq beg (point-max))
                 (member (char-syntax (char-after beg)) '(?\" ?\( ?\))))
-      (condition-case nil
+      (condition-case _
           (save-excursion
             (goto-char beg)
             (forward-sexp 1)
@@ -38,7 +38,7 @@
         (racket--escape-string-or-comment)
         (let ((done nil)
               (result nil))
-          (condition-case ()
+          (condition-case _
               (while (not done)
                 (backward-up-list)
                 (when (looking-at-p (rx ?\( (or "require" "#%require")))

racket-edit.el

@@ -224,7 +224,7 @@ point."
     (let ((first-beg nil)
           (requires nil))
       (while
-          (condition-case nil
+          (condition-case _
               (let ((end (progn (forward-sexp  1) (point)))
                     (beg (progn (forward-sexp -1) (point))))
                 (unless (equal end (point-max))
@@ -246,7 +246,7 @@ around point. This could be \"(point-min)\" if point is within no
 module form, meaning the outermost, file module."
   (save-excursion
     (racket--escape-string-or-comment)
-    (condition-case ()
+    (condition-case _
         (progn
           (while (not (racket--looking-at-module-form))
             (backward-up-list))
@@ -416,7 +416,7 @@ Only call F when the couple's sexprs are on the same line.
 
 When LISTP is true, expects couples to be `[id val]`, else `id val`."
   (save-excursion
-    (condition-case ()
+    (condition-case _
         (while t
           (when listp
             (down-list))

racket-eldoc.el

@@ -15,7 +15,7 @@
   (and (racket--cmd-open-p)
        (> (point) (point-min))
        (save-excursion
-         (condition-case nil
+         (condition-case _
              ;; The char-before and looking-at-p checks below are to
              ;; skip when the sexp is quoted or when its first elem
              ;; couldn't be a Racket function name.

racket-font-lock.el

@@ -393,7 +393,7 @@ similar, it will already be there."
 
 (defun racket--inside-complete-sexp ()
   "Return whether point is inside a complete sexp."
-  (condition-case ()
+  (condition-case _
       (save-excursion (backward-up-list) (forward-sexp 1) t)
     (error nil)))
 

racket-imenu.el

@@ -62,7 +62,7 @@ If sexp at point is a Racket module form create a submenu."
     (forward-sexp -1)))
 
 (defun racket--imenu-goto-start-of-following-sexp ()
-  (condition-case nil
+  (condition-case _
       (progn
         (forward-sexp 1)
         (let ((orig (point)))

racket-indent.el

@@ -198,7 +198,7 @@ need."
     (let ((indent-point (point))
           (state        nil))
       (racket--escape-string-or-comment)
-      (condition-case nil (backward-up-list 1) (scan-error nil))
+      (condition-case _ (backward-up-list 1) (scan-error nil))
       (while (< (point) indent-point)
         (setq state (parse-partial-sexp (point) indent-point 0)))
       (let ((strp (racket--ppss-string-p state))
@@ -366,7 +366,7 @@ Any additional, non-distinguished forms get normal indent."
                              (skip-chars-forward " \t\n")
                              (current-column)))
         (count -1))
-    (condition-case nil
+    (condition-case _
         (while (and (<= (point) indent-point)
                     (not (eobp)))
           (forward-sexp 1)

racket-repl.el

@@ -457,7 +457,7 @@ Otherwise send to current-input-port of user program."
 
 (defun racket--repl-complete-sexp-p ()
   "Is there at least one complete sexp at REPL prompt?"
-  (condition-case nil
+  (condition-case _
       (let* ((beg (racket--repl-prompt-mark-end))
              (end (save-excursion
                     (goto-char beg)

racket-visit.el

@@ -32,7 +32,7 @@ The returned string has text properties:
   an index of 0 for `get-text-property'."
   (when (racket--in-require-form-p)
     (save-excursion
-      (condition-case ()
+      (condition-case _
           (progn
             (forward-sexp 1)
             (backward-sexp 1)
@@ -43,7 +43,7 @@ The returned string has text properties:
                 ((and (pred identity) sexp)
                  (let* ((relative-p (stringp sexp))
                         (multi-in-prefix
-                         (condition-case ()
+                         (condition-case _
                              (progn
                                (backward-up-list 1)
                                (backward-sexp 2)