Enter null in DBMS_OUTPUT Buffer Size gives java.lang.NumberFormatException

See attached pic

java.lang.NumberFormatException: For input string: "null"

        at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)

        at java.lang.Long.parseLong(Long.java:410)

        at java.lang.Long.valueOf(Long.java:525)

        at \\...\\ .\\हिñçêČάй語简??한\\.zꊏꅮꌰ᠈.bQd(Unknown Source)

        at \\...\\ .\\हिñçêČάй語简??한\\.lꆙꄲ᠅ꍣ.a(Unknown Source)

        at \\...\\ .\\हिñçêČάй語简??한\\._5ꃹꈳᢇ volatile Object.a(Unknown Source)

        at com.aquafold.datastudio.queryanalyzer.tꃅꇟ⣬ꇚ new.run(Unknown Source)