Fix: Resolved NullPointerException in VersionHelper.getCurrentVersion()

[Takaranoao]

Fixed :

Caused by: java.lang.NullPointerException: Cannot invoke "java.lang.CharSequence.length()" because "this.text" is null
        at java.util.regex.Matcher.getTextLength(Matcher.java:1808) ~[?:?]
        at java.util.regex.Matcher.reset(Matcher.java:461) ~[?:?]
        at java.util.regex.Matcher.<init>(Matcher.java:256) ~[?:?]
        at java.util.regex.Pattern.matcher(Pattern.java:1180) ~[?:?]
        at at.helpch.placeholderapi.expansion.server.util.VersionHelper.getCurrentVersion(VersionHelper.java:75) ~[?:?]
        at at.helpch.placeholderapi.expansion.server.util.VersionHelper.<clinit>(VersionHelper.java:42) ~[?:?]
        ... 62 more

[Kqliber]

The NPE is coming from the fact that getCurrentVersion() is being called while MINECRAFT_VERSION has not yet been initialized (hence the NPE)

all that needs to be changed is that this field gets initialized before the method is called

[iGabyTM]

Thank you for the contribution but this was fixed on e728eb5