[CMake] [nitpick] Incorrect FILE(COPY) error message

[Sergey Zakharchenko]

Hello,

The FILE(COPY) command displays an incorrect error message when its
argyument is empty:

$ cat >x.cmake
FILE(COPY "" DESTINATION ".")

$ cmake -P x.cmake
CMake Error at x.cmake:1 (FILE):
  file INSTALL encountered an empty string input file name.

INSTALL should obviously be COPY. This happens with at least CMake
3.0.1 and 3.4.1.

Best regards,

-- 
DoubleF

P.S. I gave up on the FILE(UPLOAD) custom TLS certificate issue I
reported previously.