Fix newly reported PHPStan errors

Author: swissspidy

src/DB_Command.php

@@ -1161,6 +1161,12 @@ public function size( $args, $assoc_args ) {
 					$size_key = floor( log( (float) $row['Size'] ) / log( 1000 ) );
 					$sizes    = [ 'B', 'KB', 'MB', 'GB', 'TB' ];
 
+					if ( is_infinite( $size_key ) ) {
+						$size_key = 0;
+					}
+
+					$size_key = (int) $size_key;
+
 					$size_format = isset( $sizes[ $size_key ] ) ? $sizes[ $size_key ] : $sizes[0];
 				}