lsp-lens-mode errors if lenses are created in an empty buffer

[nbfalcon]

Describe the bug
An error is thrown if a lens from an LS is to be displayed at the end of the buffer, for example because the latter is empty.

To Reproduce
0. M-x toggle-debug-on-error

1. Create a new empty haskell file with haskell-language-server as LS (the latter sends a lens for empty buffers)
2. Observe an error

Expected behavior
Lenses should work.

Which Language Server did you use
haskell-language-server

OS
Ubuntu 20.04 LTS

Error callstack

Debugger entered--Lisp error: (wrong-type-argument integer-or-marker-p nil)
  lsp-lens--update(#<overlay in no buffer>)
  lsp-lens--show(#("module Main where\n" 0 18 (local-map (keymap (mouse-1 . #f(compiled-function () (interactive nil) #<bytecode 0x15934d4ff2ed>))) mouse-face lsp-lens-mouse-face point hand action #f(compiled-function () (interactive nil) #<bytecode 0x15934d4ff2c5>) face lsp-lens-face)) 1 (#("module Main where\n" 0 18 (face lsp-lens-face action #f(compiled-function () (interactive nil) #<bytecode 0x15934d4ff2c5>) point hand mouse-face lsp-lens-mouse-face local-map (keymap (mouse-1 . #f(compiled-function () (interactive nil) #<bytecode 0x15934d4ff2ed>)))))))
  #f(compiled-function (input0) #<bytecode 0x15934d2cc461>)((0 #<hash-table equal 3/3 0x15934df2ecf9>))
  mapcar(#f(compiled-function (input0) #<bytecode 0x15934d2cc461>) ((0 #<hash-table equal 3/3 0x15934df2ecf9>)))
  -map(#f(compiled-function (input0) #<bytecode 0x15934d2cc461>) ((0 #<hash-table equal 3/3 0x15934df2ecf9>)))
  lsp-lens--display((#<hash-table equal 3/3 0x15934df2ecf9>))
  lsp-lens-show()
  funcall-interactively(lsp-lens-show)
  call-interactively(lsp-lens-show record nil)
  command-execute(lsp-lens-show record)
  counsel-M-x-action("lsp-lens-show")
  ivy-call()
  ivy-read("M-x " ("lsp-lens-show" "ccls-code-lens-mode" "lsp" "lsp-workspace-restart" "lsp-lens-mode" "dap-disconnect" "dap-ui-inspect-repl-result" "projectile-run-eshell" "counsel-projectile-rg" "toggle-debug-on-error" "dap-debug" "counsel-rg" "git-commit-elisp-text-mode" "ert" "dap-next" "calc" "lsp-treemacs-symbols" "dap-breakpoint-add" "prettify-symbols-mode" "my/save-backtrace-buffer" "my/disassemble-sexp" "lispy-mode" "+python/open-ipython-repl" "trace-function" "ptemplate-new-project" "lsp-treemacs-call-hierarchy" "untrace-function" "lsp-avy-lens" "lsp-lens-hide" "overseer-test" "package-lint-current-buffer" "emacs-lisp-mode" "run-geiser" "+lua/open-repl" "debug-on-entry" "hack-dir-local-variables-non-file-buffer" "imenu-list" "checkdoc" "dap-ui-eval-variable-in-buffer" "flyspell-buffer" "magit-abort-dwim" "+python/open-repl" "byte-compile-file" "dap-continue" "lsp-treemacs-errors-list" "lsp-disconnect" "completion-at-point" "cancel-debug-on-entry" "lsp-shutdown-workspace" "projectile-compile-project" ...) :predicate #f(compiled-function (x) #<bytecode 0x15934cda5ab9>) :require-match t :history counsel-M-x-history :action counsel-M-x-action :keymap (keymap (67108908 . counsel--info-lookup-symbol) (67108910 . counsel-find-symbol)) :initial-input nil :caller counsel-M-x)
  counsel-M-x()
  funcall-interactively(counsel-M-x)
  call-interactively(counsel-M-x nil nil)
  command-execute(counsel-M-x)

The cause of the error
Note the overlay in no buffer part of the backtrace. This is because lsp-lens--ensure-at makes an overlay from point-at-bol to (1+ point-at-eol), which, clipped, equals point-at-bol because the buffer is empty, creating an overlay that covers no text. This overlay immediately dies, because the evaporate property is enabled for it:

(-doto (make-overlay (point-max) (1+ (point-max)))
  (overlay-put 'evaporate t)) ;; result: `overlay in no buffer`