RT3754: check for NULL pointer

Fix both the caller to error out on malloc failure, as well as the
eventual callee to handle a NULL gracefully.
Reviewed-by: NViktor Dukhovni <viktor@openssl.org>

crypto/evp/p_lib.c

@@ -261,7 +261,7 @@ int EVP_PKEY_set_type_str(EVP_PKEY *pkey, const char *str, int len)
 
 int EVP_PKEY_assign(EVP_PKEY *pkey, int type, void *key)
 {
-    if (!EVP_PKEY_set_type(pkey, type))
+    if (pkey == NULL || !EVP_PKEY_set_type(pkey, type))
         return 0;
     pkey->pkey.ptr = key;
     return (key != NULL);

crypto/evp/pmeth_gn.c

@@ -96,12 +96,17 @@ int EVP_PKEY_paramgen(EVP_PKEY_CTX *ctx, EVP_PKEY **ppkey)
         return -1;
     }
 
-    if (!ppkey)
+    if (ppkey == NULL)
         return -1;
 
-    if (!*ppkey)
+    if (*ppkey == NULL)
         *ppkey = EVP_PKEY_new();
 
+    if (*ppkey == NULL) {
+        EVPerr(EVP_F_EVP_PKEY_PARAMGEN, ERR_R_MALLOC_FAILURE);
+        return -1;
+    }
+
     ret = ctx->pmeth->paramgen(ctx, *ppkey);
     if (ret <= 0) {
         EVP_PKEY_free(*ppkey);