warning: address of array 'key->printf' will always evaluate to 'true' [-Wpointer-bool-conversion]

[ryandesign]

Recent clang produces these warnings:

fitswrite.c:455:34: warning: address of array 'key->printf' will always evaluate to 'true' [-Wpointer-bool-conversion]
  455 |             fprintf(stream, key->printf?key->printf:"%d", (int)*ptr);
      |                             ~~~~~^~~~~~~
fitswrite.c:541:34: warning: address of array 'key->printf' will always evaluate to 'true' [-Wpointer-bool-conversion]
  541 |             fprintf(stream, key->printf?key->printf:"%d", (int)*ptr);
      |                             ~~~~~^~~~~~~