Encode INTEGER correctly.

If an ASN1_INTEGER structure is allocated but not explicitly set encode
it as zero: don't generate an invalid zero length INTEGER.
(cherry picked from commit 1643edc63c3e15b6db5a15a728bc288f2cc2bbc7)

crypto/asn1/a_int.c

@@ -116,7 +116,7 @@ int i2c_ASN1_INTEGER(ASN1_INTEGER *a, unsigned char **pp)
 	int pad=0,ret,i,neg;
 	unsigned char *p,*n,pb=0;
 
-	if ((a == NULL) || (a->data == NULL)) return(0);
+	if (a == NULL) return(0);
 	neg=a->type & V_ASN1_NEG;
 	if (a->length == 0)
 		ret=1;