Check for empty input before evaluating expr

Author: tomdl89

evil-common.el

@@ -2042,7 +2042,8 @@ or a marker object pointing nowhere."
   "Eval INPUT and return stringified result, if of a suitable type.
 If INPUT starts with a number, +, -, or . use `calc-eval' instead."
   (let* ((first-char (car (remove ?\s (string-to-list input))))
-         (calcable-p (or (<= ?0 first-char ?9) (memq first-char '(?- ?+ ?.))))
+         (calcable-p (and first-char (or (<= ?0 first-char ?9)
+                                         (memq first-char '(?- ?+ ?.)))))
          (result (if calcable-p
                      (let ((calc-multiplication-has-precedence nil))
                        (calc-eval input))