Fix some comment typos
diff --git a/library/x509_crt.c b/library/x509_crt.c
index 02183e5..474c244 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -1631,7 +1631,7 @@
 
 /*
  * Check that the given certificate is not revoked according to the CRL.
- * Skip validation is no CRL for the given CA is present.
+ * Skip validation if no CRL for the given CA is present.
  */
 static int x509_crt_verifycrl( mbedtls_x509_crt *crt, mbedtls_x509_crt *ca,
                                mbedtls_x509_crl *crl_list,