spool.c:parseheader() - remove unnecessary checks for NULL

The static function imap/spool.c:parseheader() is called from only one place.

The passed parameters headname, contents and rawvalue from that place are not
NULL, so there is no need to check within parseheader() if these parameters
are NULL.

imap/spool.c

@@ -110,6 +110,7 @@ typedef enum {
 
    on error, returns < 0
 */
+__attribute__((nonnull(3,4,5)))
 static int parseheader(struct protstream *fin, FILE *fout,
                        char **headname, char **contents,
                        char **rawvalue,
@@ -291,9 +292,9 @@ static int parseheader(struct protstream *fin, FILE *fout,
     if (c != EOF) prot_ungetc(c, fin);
 
     /* and we didn't get a header */
-    if (headname != NULL) *headname = NULL;
-    if (contents != NULL) *contents = NULL;
-    if (rawvalue != NULL) *rawvalue = NULL;
+    *headname = NULL;
+    *contents = NULL;
+    *rawvalue = NULL;
 
     return r;
 
@@ -303,9 +304,9 @@ static int parseheader(struct protstream *fin, FILE *fout,
     /* Note: xstrdup()ing the string ensures we return
      * a minimal length string with no allocation slack
      * at the end */
-    if (headname != NULL) *headname = xstrdup(name.s);
-    if (contents != NULL) *contents = xstrdup(body.s);
-    if (rawvalue != NULL) *rawvalue = xstrdup(raw.s);
+    *headname = xstrdup(name.s);
+    *contents = xstrdup(body.s);
+    *rawvalue = xstrdup(raw.s);
 
     return 0;
 }