fix unbound_variable

poc

@@ -163,6 +163,7 @@ function on_error {
 function on_pipe {
   trap - RETURN
   local tmp_error regex source lineno
+  miaou_debug "<on_pipe sub_pid=$BASHPID pid=$$>"
 
   error_source=("${BASH_SOURCE[@]}")
   error_lineno=("${BASH_LINENO[@]}")
@@ -171,7 +172,8 @@ function on_pipe {
   unset 'error_source[-1]' 'error_lineno[-1]' 'error_funcname[-1]'
   unset 'error_source[-1]' 'error_lineno[-1]' 'error_funcname[-1]'
 
-  mapfile -t tmp_error <"$MIAOU_BASH_ERROR"
+  miaou_debug '<load_tmp_error/>' && mapfile -t tmp_error <"$MIAOU_BASH_ERROR"
+
   last_error="${tmp_error[-1]}"
   regex='^(.*): line ([0-9]+): miaou_error: SUBSHELL_ERROR ([0-9]+) payload: (.*)$'
   if [[ $last_error =~ $regex ]]; then
@@ -187,7 +189,7 @@ function on_pipe {
     failure_code=141
     failure_type="PIPE_ERROR"
   fi
-  miaou_debug "<on_pipe code=$failure_code sub_pid=$BASHPID pid=$$ />"
+  miaou_debug "</on_pipe/>"
   builtin exit "$failure_code"
 }
 
@@ -249,7 +251,9 @@ function on_exit {
 
   miaou_debug "<on_exit code=$code>"
 
-  [[ ! -v tmp_error ]] && mapfile -t tmp_error <"$MIAOU_BASH_ERROR"
+  [[ ! -v tmp_error ]] &&
+    miaou_debug '<load_tmp_error/>' &&
+    mapfile -t tmp_error <"$MIAOU_BASH_ERROR"
 
   if [[ -v failure_type && "$failure_type" == 'RETURN' ]]; then
     last_error="${tmp_error[-1]}"
@@ -274,13 +278,10 @@ function on_exit {
         regex='^(.*): line ([0-9]+): (.*): unbound variable$'
         if [[ "$last_error" =~ $regex ]]; then
           local source line payload
+
           source="${BASH_REMATCH[1]}"
           line="${BASH_REMATCH[2]}"
           payload="${BASH_REMATCH[3]}"
-          miaou_debug "<unbound_variable source=${source} line=${line} payload={${payload}} >"
-          failure_code=$code
-          failure_type='UNBOUND_VARIABLE'
-          failure_payload="${BASH_REMATCH[3]}"
           error_source=("${BASH_SOURCE[@]}")
           error_lineno=("${BASH_LINENO[@]}")
           error_funcname=("${FUNCNAME[@]}")
@@ -290,6 +291,11 @@ function on_exit {
           error_source=("$source" "${error_source[@]}")
           error_lineno=("$line" "${error_lineno[@]}")
           error_funcname=("${error_funcname[@]}" '<main>')
+
+          failure_code=$code
+          failure_type='UNBOUND_VARIABLE'
+          failure_payload=$payload
+          miaou_debug "<unbound_variable source=${source} line=${line} payload={${failure_payload}}>"
         fi
       fi
       miaou_debug "</on_exit_tmp_error>"