1、【修改】一处注释说明不准确地方，并完善API说明文档中一处有歧义的内容。

Signed-off-by: armink <armink.ztl@gmail.com>

docs/zh/api.md

@@ -77,8 +77,8 @@ FlashErrCode flash_set_env(const char *key, const char *value)
 FlashErrCode flash_save_env(void)
 ```
 
-#### 1.2.6 恢复环境变量
-将内存中的环境变量表恢复为默认值。
+#### 1.2.6 重置环境变量
+将内存中的环境变量表重置为默认值。
 
 ```C
 FlashErrCode flash_env_set_default(void)

flash/src/flash_env.c

@@ -394,7 +394,7 @@ FlashErrCode flash_del_env(const char *key){
 }
 
 /**
- * Set an environment variable. If it value is NULL, delete it.
+ * Set an environment variable. If it value is empty, delete it.
  * If not find it in environment variables table, then create it.
  *
  * @param key environment variable name
@@ -407,7 +407,7 @@ FlashErrCode flash_set_env(const char *key, const char *value) {
 
     FLASH_ASSERT(env_cache);
 
-    /* if value is null, delete it */
+    /* if ENV value is empty, delete it */
     if (*value == NULL) {
         result = flash_del_env(key);
     } else {

flash/src/flash_env_wl.c

@@ -427,7 +427,7 @@ FlashErrCode flash_del_env(const char *key){
 }
 
 /**
- * Set an environment variable. If it value is NULL, delete it.
+ * Set an environment variable. If it value is empty, delete it.
  * If not find it in environment variables table, then create it.
  *
  * @param key environment variable name
@@ -440,7 +440,7 @@ FlashErrCode flash_set_env(const char *key, const char *value) {
 
     FLASH_ASSERT(env_cache);
 
-    /* if value is null, delete it */
+    /* if ENV value is empty, delete it */
     if (*value == NULL) {
         result = flash_del_env(key);
     } else {