warning: address of array 'key->printf' will always evaluate to 'true'

[ryandesign]

These warnings appear when building 3.24.2:

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