Fix for bug #30088: Can't disable myisam-recover by a value of "".

  - test result.

Problem: we don't proper handle "" value of the --myisam-recover option.

Fix: turn off myisam recovering if --myisam-recover="" is set.

mysql-test/r/show_check.result

@@ -1118,4 +1118,7 @@ select 1 from information_schema.tables limit 1;
 show status like 'slow_queries';
 Variable_name	Value
 Slow_queries	2
+show variables like 'myisam_recover_options';
+Variable_name	Value
+myisam_recover_options	OFF
 End of 5.0 tests

mysql-test/t/show_check-master.opt

---log-slow-queries --log-long-format --log-queries-not-using-indexes
+--log-slow-queries --log-long-format --log-queries-not-using-indexes --myisam-recover=""

mysql-test/t/show_check.test

@@ -782,4 +782,9 @@ show variables like "log_queries_not_using_indexes";
 select 1 from information_schema.tables limit 1;
 show status like 'slow_queries';
 
+#
+# Bug #30088: Can't disable myisam-recover by a value of ""
+#
+show variables like 'myisam_recover_options';
+
 --echo End of 5.0 tests

sql/mysqld.cc

@@ -7241,11 +7241,16 @@ get_one_option(int optid, const struct my_option *opt __attribute__((unused)),
 #endif /* HAVE_INNOBASE_DB */
   case OPT_MYISAM_RECOVER:
   {
-    if (!argument || !argument[0])
+    if (!argument)
     {
       myisam_recover_options=    HA_RECOVER_DEFAULT;
       myisam_recover_options_str= myisam_recover_typelib.type_names[0];
     }
+    else if (!argument[0])
+    {
+      myisam_recover_options= HA_RECOVER_NONE;
+      myisam_recover_options_str= "OFF";
+    }
     else
     {
       myisam_recover_options_str=argument;