Fix parameter validation order in UTF32Reader to catch negative length

Co-authored-by: pjfanning <11783444+pjfanning@users.noreply.github.com>

Author: Copilot

src/main/java/tools/jackson/core/io/UTF32Reader.java

@@ -114,13 +114,13 @@ public int read() throws IOException {
     public int read(char[] cbuf, int start, int len) throws IOException
     {
         Objects.requireNonNull(cbuf, "cbuf");
-        // Already EOF?
-        if (_buffer == null) { return -1; }
-        if (len < 1) { return len; }
         // Let's then ensure there's enough room...
         if (start < 0 || len < 0 || start > (cbuf.length - len)) {
             reportBounds(cbuf, start, len);
         }
+        // Already EOF?
+        if (_buffer == null) { return -1; }
+        if (len < 1) { return len; }
 
         int outPtr = start;
         final int outEnd = len+start;