Fix an incoherent test.

Pointer 'o' is set inside a local buffer, so it can't be NULL.
Also fix coding style and add comments

Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4754)

crypto/objects/obj_dat.c

diff --git a/crypto/objects/obj_dat.c b/crypto/objects/obj_dat.c
index 3f65d37..06a3fb3 100644
--- a/crypto/objects/obj_dat.c
+++ b/crypto/objects/obj_dat.c
@@ -632,6 +632,10 @@
     return p;
 }
 
+/*
+ * Parse a BIO sink to create some extra oid's objects.
+ * Line format:<OID:isdigit or '.']><isspace><SN><isspace><LN>
+ */
 int OBJ_create_objects(BIO *in)
 {
     char buf[512];
@@ -653,9 +657,9 @@
             *(s++) = '\0';
             while (ossl_isspace(*s))
                 s++;
-            if (*s == '\0')
+            if (*s == '\0') {
                 s = NULL;
-            else {
+            } else {
                 l = s;
                 while (*l != '\0' && !ossl_isspace(*l))
                     l++;
@@ -663,14 +667,17 @@
                     *(l++) = '\0';
                     while (ossl_isspace(*l))
                         l++;
-                    if (*l == '\0')
+                    if (*l == '\0') {
                         l = NULL;
-                } else
+                    }
+                } else {
                     l = NULL;
+                }
             }
-        } else
+        } else {
             s = NULL;
-        if ((o == NULL) || (*o == '\0'))
+        }
+        if (*o == '\0')
             return num;
         if (!OBJ_create(o, s, l))
             return num;