Improve error handling of TokenBuffer wrt malformed input (EOF handling) (#4260)

Author: cowtowncoder

src/main/java/com/fasterxml/jackson/databind/util/TokenBuffer.java

@@ -7,6 +7,7 @@
 
 import com.fasterxml.jackson.core.*;
 import com.fasterxml.jackson.core.base.ParserMinimalBase;
+import com.fasterxml.jackson.core.io.JsonEOFException;
 import com.fasterxml.jackson.core.io.NumberInput;
 import com.fasterxml.jackson.core.json.JsonWriteContext;
 import com.fasterxml.jackson.core.util.ByteArrayBuilder;
@@ -1161,7 +1162,8 @@ public void copyCurrentStructure(JsonParser p) throws IOException
             t = p.nextToken();
             // fall-through to copy the associated value
         } else if (t == null) {
-            throw new IllegalStateException("No token available from argument `JsonParser`");
+            // 13-Dec-2024, tatu: For some unexpected EOF cases we may end up here, so:
+            throw new JsonEOFException(p, null, "Unexpected end-of-input");
         }
 
         // We'll do minor handling here to separate structured, scalar values,