qcacld-3.0: Fix possible NULL dereference

Potential NULL pointer dereference in below function:
 wma_get_rx_chainmask()

Add wmi_handle NULL check in the above function.

Change-Id: I34965388a4782236c3bc5158098b5b066833c066
CRs-Fixed: 2536323

core/wma/src/wma_main.c

@@ -9583,7 +9583,12 @@ QDF_STATUS wma_get_rx_chainmask(uint8_t pdev_id, uint32_t *chainmask_2g,
 	struct wlan_psoc_host_mac_phy_caps *mac_phy_cap;
 	uint8_t total_mac_phy_cnt;
 	struct target_psoc_info *tgt_hdl;
+
 	tp_wma_handle wma_handle = cds_get_context(QDF_MODULE_ID_WMA);
+	if (!wma_handle) {
+		wma_err("wma_handle is NULL");
+		return QDF_STATUS_E_INVAL;
+	}
 
 	tgt_hdl = wlan_psoc_get_tgt_if_handle(wma_handle->psoc);
 	if (!tgt_hdl) {