Any Help ? every time AST_FRAME_DTMF_END .Asterisk-11.5.1 ap

Any Help ? every time AST_FRAME_DTMF_END .Asterisk-11.5.1 app_confbridge.c

it works fine in asterisk-11.5.1/funcs/func_frame_trace.c

while (ast_waitfor(participant->chan, 1)) { 
            

ast_verb(3,"\n f Searching \n "); 
                 
            f = ast_read(participant->chan); 
            if (!f) { 
            ast_verb(3,"\n !f not found "); 
            res = 0; 
            break; 
            } 
            if(f){   
            digitpass=f->subclass.integer;   
            ast_verb(3,"\n digit pass is : digitpass=f->subclass.integer:%d  :%d f->frametype:%d \n ",digitpass,f->subclass.integer,f->frametype); 
            int type=f->frametype;   
     
            switch(type){ 
            case 1: 
            ast_verbose("confbridgeFrameType DTMF END\n"); 
            ast_verbose("Digit: %d\n", f->subclass.integer); 
            ast_verbose("\n AST_FRAME_DTMF_END:sabse pass Digit[%d] and f->frametype:[%d] to confbridge_run \n",f->subclass.integer,f->frametype); 
            break; 
             
            case 5: 
            ast_verbose("confbridgeFrameType DTMF END\n"); 
            ast_verbose("Digit: %d\n", f->subclass.integer); 
            ast_verbose("\n AST_FRAME_DTMF_END:sabse pass Digit[%d] and f->frametype:[%d] to confbridge_run \n",f->subclass.integer,f->frametype); 
            break; 
             
            case 12: 
            ast_verbose("FrameTypeTMF BEGIN \n"); 
            ast_verbose("Digit: %d\n", f->subclass.integer); 
            ast_verb(3,"\n AST_FRAME_DTMF_BEGIN: sabse pass Digit[%d] and f->frametype:[%d] to confbridge_run \n",f->subclass.integer,f->frametype); 
            //int passval=f->subclass.integer;   
            digitpass=f->subclass.integer; 
            break; 
            } 
             
            ast_frfree(f); 
            } 
    }  //end of while 

===============

refer: asteriks-11.5.1/funcs/func_frame_trace.c
================
=====Output ====
<--Read on Channel SIP/6017-00000000
FrameType: DTMF END
Digit: 50
AST_FRAME_DTMF_END:sabse pass Digit[50] and frame->frametype:[1] to confbridge_run 

====
issue,
participant->chan ast_waitfor(chan,

f Searching

<–Read on Channel SIP/6017-00000000
FrameType: NULL

AST_FRAME_NULL: pass Digit[0] and frame->frametype:[5] to confbridge_run
Src: NOT PRESENT

-- 

digit pass is : digitpass=f->subclass.integer:0 :0 f->frametype:5
confbridgeFrameType DTMF END
Digit: 0

AST_FRAME_DTMF_END:sabse pass Digit[0] and f->frametype:[5] to confbridge_run

f Searching
<–Read on Channel SIP/6017-00000000
FrameType: NULL

AST_FRAME_NULL: sabse pass Digit[0] and frame->frametype:[5] to confbridge_run
Src: NOT PRESENT

-- 

digit pass is : digitpass=f->subclass.integer:0 :0 f->frametype:5
confbridgeFrameType DTMF END
Digit: 0