fabric: only strip the starting '/' from input when it is actually there

Author: jpenilla

cloud-minecraft/cloud-fabric/src/main/java/cloud/commandframework/fabric/FabricExecutor.java

@@ -79,7 +79,9 @@ final class FabricExecutor<C, S extends CommandSource> implements Command<S> {
     @Override
     public int run(final @NonNull CommandContext<S> ctx) {
         final S source = ctx.getSource();
-        final String input = ctx.getInput().substring(1);
+        final String input = ctx.getInput().startsWith("/")
+                ? ctx.getInput().substring(1)
+                : ctx.getInput();
         final C sender = this.manager.getCommandSourceMapper().apply(source);
         this.manager.executeCommand(sender, input).whenComplete(this.getResultConsumer(source, sender));
         return com.mojang.brigadier.Command.SINGLE_SUCCESS;