/api/v1/firewall/nat/outbound/mapping throws error when no mappings exist

[jaredhendrickson13]

Describe the bug
When adding a new outbound NAT mapping to a pfSense instance with no outbound NAT mappings, an error is thrown.

Expected behavior
The outbound NAT mapping should be created.

Screenshots or Response

Fatal error: Uncaught TypeError: count(): Argument #1 ($value) must be of type Countable|array, null given in /etc/inc/api/models/APIFirewallNATOutboundMappingCreate.inc:39\nStack trace:\n#0 /etc/inc/api/framework/APIModel.inc(216): APIFirewallNATOutboundMappingCreate->action()\n#1 /etc/inc/api/endpoints/APIFirewallNATOutboundMapping.inc(28): APIModel->call()\n#2 /etc/inc/api/framework/APIEndpoint.inc(63): APIFirewallNATOutboundMapping->post()\n#3 /usr/local/www/api/v1/firewall/nat/outbound/mapping/index.php(3): APIEndpoint->listen()\n#4 {main}\n  thrown in /etc/inc/api/models/APIFirewallNATOutboundMappingCreate.inc on line 39\nPHP ERROR: Type: 1, File: /etc/inc/api/models/APIFirewallNATOutboundMappingCreate.inc, Line: 39, Message: Uncaught TypeError: count(): Argument #1 ($value) must be of type Countable|array, null given in /etc/inc/api/models/APIFirewallNATOutboundMappingCreate.inc:39\nStack trace:\n#0 /etc/inc/api/framework/APIModel.inc(216): APIFirewallNATOutboundMappingCreate->action()\n#1 /etc/inc/api/endpoints/APIFirewallNATOutboundMapping.inc(28): APIModel->call()\n#2 /etc/inc/api/framework/APIEndpoint.inc(63): APIFirewallNATOutboundMapping->post()\n#3 /usr/local/www/api/v1/firewall/nat/outbound/mapping/index.php(3): APIEndpoint->listen()\n#4 {main}\n  thrown"

pfSense Version & Package Version:

• pfSense Version: 2.7.0, 23.05
• Package Version v1.6.1 (pre-v1.6.0 is not effected.)

Affected Endpoints:

• URL: /api/v1/firewall/nat/outbound/mapping

Additional context
Add any other context about the problem here.