Fix #2794, Replace zero values for pointers with NULL

Author: myc-yang

modules/es/fsw/src/cfe_es_apps.c

@@ -579,7 +579,7 @@ int32 CFE_ES_GetTaskFunction(CFE_ES_TaskEntryFuncPtr_t *FuncPtr)
         if (TaskRecPtr != NULL)
         {
             EntryFunc = TaskRecPtr->EntryFunc;
-            if (CFE_RESOURCEID_TEST_DEFINED(TaskRecPtr->AppId) && EntryFunc != 0)
+            if (CFE_RESOURCEID_TEST_DEFINED(TaskRecPtr->AppId) && EntryFunc != NULL)
             {
                 ReturnCode = CFE_SUCCESS;
             }

modules/es/fsw/src/cfe_es_generic_pool.c

@@ -550,7 +550,7 @@ int32 CFE_ES_GenPoolRebuild(CFE_ES_GenPoolRecord_t *PoolRecPtr)
             /* Test if block is deallocated */
             BucketId  = BdPtr->Allocated - CFE_ES_MEMORY_DEALLOCATED;
             BucketPtr = CFE_ES_GenPoolGetBucketState(PoolRecPtr, BucketId);
-            if (BucketPtr != 0)
+            if (BucketPtr != NULL)
             {
                 IsDeallocatedBlock = true;
             }

modules/es/fsw/src/cfe_es_mempool.c

@@ -52,7 +52,7 @@
      & ((struct {      \
            char Byte;  \
            type Align; \
-       } *)0)          \
+       } *)NULL)          \
            ->Align)
 
 /*****************************************************************************/

modules/sb/fsw/src/cfe_sb_util.c

@@ -49,7 +49,7 @@ void *CFE_SB_GetUserData(CFE_MSG_Message_t *MsgPtr)
     if (MsgPtr == NULL)
     {
         CFE_ES_WriteToSysLog("%s: Failed invalid arguments\n", __func__);
-        return 0;
+        return NULL;
     }
 
     BytePtr = (uint8 *)MsgPtr;

modules/tbl/fsw/src/cfe_tbl_dispatch.c

@@ -121,7 +121,7 @@ const CFE_TBL_CmdHandlerTblRec_t CFE_TBL_CmdHandlerTbl[] = {
                   CFE_TBL_CMD_MSGTYPE),
 
     /* list terminator (keep last) */
-    { 0, 0, 0, NULL, CFE_TBL_TERM_MSGTYPE }
+    { NULL, 0, 0, NULL, CFE_TBL_TERM_MSGTYPE }
 };
 
 /******************************************************************************/