The metadata of the table and family should not be an empty string

If the metadata of the table is set to null, the metadata will be removed. The code is:

https://github.com/apache/hbase/blob/b07549febb462b072792659051c64bb54d122771/hbase-client/src/main/java/org/apache/hadoop/hbase/client/TableDescriptorBuilder.java#L721

But if set metadata as empty string, serious errors may occur. Some metadata is number,
it will throw a NumberFormatException when converting empty string to a number. If the exception is thrown when the region is initialized, all regions of the table will be in RIT.

The following command can reproduced this issue. Note: Please execute in the test environment.

alter 'test_table', CONFIGURATION => {'hbase.rs.cachecompactedblocksonwrite.threshold' => ''}