Fixed compilation warnings due to missing return statements

keyboard/ergodox_ez/keymaps/tm2030/keymap.c

@@ -216,7 +216,7 @@ const macro_t *action_get_macro(keyrecord_t *record, uint8_t id, uint8_t opt)
 
 // Runs just one time when the keyboard initializes.
 void * matrix_init_user(void) {
-
+    return NULL;
 };
 
 // Runs constantly in the background, in a loop.
@@ -238,4 +238,5 @@ void * matrix_scan_user(void) {
     if (host_keyboard_leds() & (1<<USB_LED_CAPS_LOCK)) {
       ergodox_right_led_3_on();
     }
+    return NULL;
 };