app_voicemail: Avoid always true when using pointer address.

clang 4.0 warned about this.

ASTERISK-27635

Change-Id: I213f230607d7fbe97c0f5f2d60da9cbf5a2d8231

apps/app_voicemail.c

@@ -3499,7 +3499,7 @@ static struct vm_state *get_vm_state_by_imapuser(const char *user, int interacti
 	if (interactive) {
 		struct vm_state *vms;
 		pthread_once(&ts_vmstate.once, ts_vmstate.key_init);
-		if ((vms = pthread_getspecific(ts_vmstate.key)) && vms->imapuser && !strcmp(vms->imapuser, user)) {
+		if ((vms = pthread_getspecific(ts_vmstate.key)) && !strcmp(vms->imapuser, user)) {
 			return vms;
 		}
 	}
@@ -3513,10 +3513,6 @@ static struct vm_state *get_vm_state_by_imapuser(const char *user, int interacti
 		if (vlist->vms->imapversion != imapversion) {
 			continue;
 		}
-		if (!vlist->vms->imapuser) {
-			ast_debug(3, "error: imapuser is NULL for %s\n", user);
-			continue;
-		}
 		if (!strcmp(vlist->vms->imapuser, user) && (interactive == 2 || vlist->vms->interactive == interactive)) {
 			AST_LIST_UNLOCK(&vmstates);
@@ -3539,7 +3535,7 @@ static struct vm_state *get_vm_state_by_mailbox(const char *mailbox, const char
 	if (interactive) {
 		struct vm_state *vms;
 		pthread_once(&ts_vmstate.once, ts_vmstate.key_init);
-		if ((vms = pthread_getspecific(ts_vmstate.key)) && vms->username && vms->context &&
+		if ((vms = pthread_getspecific(ts_vmstate.key)) &&
 		    !strcmp(vms->username,mailbox) && !strcmp(vms->context, local_context)) {
 			return vms;
 		}
@@ -3554,10 +3550,6 @@ static struct vm_state *get_vm_state_by_mailbox(const char *mailbox, const char
 		if (vlist->vms->imapversion != imapversion) {
 			continue;
 		}
-		if (!vlist->vms->username || !vlist->vms->context) {
-			ast_debug(3, "error: username is NULL for %s\n", mailbox);
-			continue;
-		}
 		ast_debug(3, "comparing mailbox %s@%s (i=%d) to vmstate mailbox %s@%s (i=%d)\n", mailbox, local_context, interactive, vlist->vms->username, vlist->vms->context, vlist->vms->interactive);