[KYUUBI #2354] Fix NPE in process builder log capture thread

### _Why are the changes needed?_

I saw NPE in UT.
```
Exception in thread "process-logger-capture: Thread-1972" java.lang.NullPointerException
	at org.apache.kyuubi.engine.ProcBuilder.$anonfun$start$1(ProcBuilder.scala:204)
	at java.base/java.lang.Thread.run(Thread.java:829)
```

For BufferedReader::readLine method,
```
Returns:
A String containing the contents of the line, not including any line-termination characters, or null if the end of the stream has been reached
```

### _How was this patch tested?_
- [ ] Add some test cases that check the changes thoroughly including negative and positive cases if possible

- [ ] Add screenshots for manual tests if appropriate

- [ ] [Run test](https://kyuubi.apache.org/docs/latest/develop_tools/testing.html#running-tests) locally before make a pull request

Closes #2354 from turboFei/npe_line_read.

Closes #2354

2671657 [Fei Wang] Fix npe in log capture thread

Authored-by: Fei Wang <fwang12@ebay.com>
Signed-off-by: ulysses-you <ulyssesyou@apache.org>

Author: turboFei

kyuubi-server/src/main/scala/org/apache/kyuubi/engine/ProcBuilder.scala

@@ -196,12 +196,12 @@ trait ProcBuilder {
         val maxErrorSize = conf.get(KyuubiConf.ENGINE_ERROR_MAX_SIZE)
         while (true) {
           if (reader.ready()) {
-            var line: String = reader.readLine.trim
+            var line: String = reader.readLine()
             if (containsException(line) &&
               !line.contains("at ") && !line.startsWith("Caused by:")) {
               val sb = new StringBuilder(line)
               error = KyuubiSQLException(sb.toString() + s"\n See more: $engineLog")
-              line = reader.readLine().trim
+              line = reader.readLine()
               while (sb.length < maxErrorSize && line != null &&
                 (containsException(line) ||
                   line.startsWith("\tat ") ||