Wrong type argument: number-or-marker-p, nil with eldoc-echo-area-use-multiline-p set to a number

[bcc32]

eldoc-echo-area-use-multiline-p may be set to a positive number to specify at most how many lines the user wants Eldoc to take up (either as an absolute number of lines, or as a fraction of the emacs frame height). However, when set this way, merlin-eldoc does not work correctly, and produces the following error when hovering over any symbol:

eldoc error: (wrong-type-argument number-or-marker-p nil) [6 times]

This seems to be due to the definition of merlin-eldoc-max-lines, which assumes a symbol-typed value of eldoc-echo-area-use-multiline-p (and becomes unexpectedly nil if the latter is not a symbol).