wlan: Fix issues found by static code analysis in SAP

Fix the issues reported by static code analysis tool

Change-Id: I42786698f28c8decae20d69a39084e3b27905501
CRs-Fixed: 642583
diff --git a/CORE/SAP/src/sapChSelect.c b/CORE/SAP/src/sapChSelect.c
index b5caadb..dc363bc 100644
--- a/CORE/SAP/src/sapChSelect.c
+++ b/CORE/SAP/src/sapChSelect.c
@@ -537,6 +537,13 @@
     tSapSpectChInfo *pExtSpectCh = NULL;
     v_S31_t rssi;
 
+    if (NULL == pSpectCh)
+    {
+        VOS_TRACE( VOS_MODULE_ID_SAP, VOS_TRACE_LEVEL_ERROR,
+                   "%s: pSpectCh is NULL", __func__);
+        return;
+    }
+
     switch(pSpectCh->chNum)
     {
         case CHANNEL_1: