Various optimizations for nullity checks

[Katsute]

https://github.com/KatsuteDev/Mal4J/blob/bf3dcd641afbba5ec5c4937d20c4ffd808c3c00e/src/main/java/dev/katsute/mal4j/Json.java#L276-L299

Return null instead of throwing a NPE.

Use .valueOf rather than .parse, try catch on NFE.

https://github.com/KatsuteDev/Mal4J/blob/bf3dcd641afbba5ec5c4937d20c4ffd808c3c00e/src/main/java/dev/katsute/mal4j/Json.java#L301-L303

Return an empty JsonObject if null, this will protect against chained nulls.

https://github.com/KatsuteDev/Mal4J/blob/bf3dcd641afbba5ec5c4937d20c4ffd808c3c00e/src/main/java/dev/katsute/mal4j/Json.java#L313-L319

Return an empty array if null, this will protect against null loops.

Various as methods need to be rewritten to return null if null object.

These changes should remove the need for requireNonNull.

[Katsute]

@mashiro-san create a branch optimization

[ghost]

@Katsute I have created a new branch optimization@bf3dcd6