Avoid exception messages while autocomplete initialization in export.sh

export.sh

@@ -147,6 +147,7 @@ __cleanup() {
     unset ESP_PYTHON
     unset SOURCE_ZSH
     unset SOURCE_BASH
+    unset WARNING_MSG
 
     unset __realpath
     unset __main
@@ -177,7 +178,9 @@ __enable_autocomplete() {
         eval "$(env _IDF.PY_COMPLETE=$SOURCE_ZSH idf.py)" || echo "WARNING: Failed to load shell autocompletion for zsh version: $ZSH_VERSION!"
     elif [ -n "${BASH_SOURCE-}" ]
     then
-        eval "$(env LANG=en _IDF.PY_COMPLETE=$SOURCE_BASH idf.py)"  || echo "WARNING: Failed to load shell autocompletion for bash version: $BASH_VERSION!"
+        WARNING_MSG="WARNING: Failed to load shell autocompletion for bash version: $BASH_VERSION!"
+        [[ ${BASH_VERSINFO[0]} -lt 4 ]] && { echo "$WARNING_MSG"; return; }
+        eval "$(env LANG=en _IDF.PY_COMPLETE=$SOURCE_BASH idf.py)"  || echo "$WARNING_MSG"
     fi
 }