3.1.2 bugfixes (see long description)

- add messages in /rank and /rankup for when the configuration has a rankup to a non-existent rank.
- add invalid rankup message
- fix error for placeholders when prestiging is disabled
- add message for when a rank has no requirements

src/main/java/sh/okx/rankup/ranks/Rank.java

@@ -11,6 +11,7 @@ import sh.okx.rankup.messages.MessageBuilder;
 import sh.okx.rankup.requirements.DeductibleRequirement;
 import sh.okx.rankup.requirements.Operation;
 import sh.okx.rankup.requirements.Requirement;
+import sh.okx.rankup.requirements.operation.AllOperation;
 
 import java.util.HashSet;
 import java.util.List;
@@ -39,6 +40,9 @@ public class Rank {
     if (requirementsSection != null) {
       requirements = plugin.getRequirementRegistry().getRequirements(requirementsSection);
       operation = plugin.getOperationRegistry().getOperation(section.getString("operation"));
+    } else if(section.contains("next")) {
+      plugin.getLogger().severe("Rank " + section.getName() + " has no requirements.");
+      return null;
     }
 
     return new Rank(plugin,