After this commit libCurl is unable to handle P12 (PKCS#12) certificates, see comment of AStankov to the commit.
On head revision this code is moved to openssl.c near line 533
in case of “case SSL_FILETYPE_PKCS12:” code will go to “default:” statement anyway, independently of P12 certificate check.
The error will be "not supported file type '%s' for certificate"
Additional “break” is needed between line 533 and 541