[KYUUBI apache#6126] Filter blank engine home env

# 🔍 Description
## Issue References 🔗

This pull request fixes apache#6126

## Describe Your Solution 🔧

Filter blank engine home env

## Types of changes 🔖

- [X] Bugfix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing functionality to change)

## Test Plan 🧪

#### Behavior Without This Pull Request ⚰️

#### Behavior With This Pull Request 🎉

#### Related Unit Tests

---

# Checklist 📝

- [X] This patch was not authored or co-authored using [Generative Tooling](https://www.apache.org/legal/generative-tooling.html)

**Be nice. Be informative.**

Closes apache#6127 from wForget/KYUUBI-6126.

Closes apache#6126

a42a8a6 [wforget] fix typo
55d2bfc [wforget] [KYUUBI-6126] Filter blank engine home env

Authored-by: wforget <[email protected]>
Signed-off-by: Cheng Pan <[email protected]>
(cherry picked from commit 9e7f2d0)

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

@@ -26,6 +26,7 @@ import scala.collection.JavaConverters._
 
 import com.google.common.annotations.VisibleForTesting
 import com.google.common.collect.EvictingQueue
+import org.apache.commons.lang3.StringUtils
 import org.apache.commons.lang3.StringUtils.containsIgnoreCase
 
 import org.apache.kyuubi._
@@ -306,7 +307,7 @@ trait ProcBuilder {
    *
    * Take Spark as an example, we first lookup the SPARK_HOME from user specified environments.
    * If not found, we assume that it is a dev environment and lookup the kyuubi-download's output
-   * directly. If not found again, a `KyuubiSQLException` will be raised.
+   * directory. If not found again, a `KyuubiSQLException` will be raised.
    * In summarize, we walk through
    *   `kyuubi.engineEnv.SPARK_HOME` ->
    *   System.env("SPARK_HOME") ->
@@ -319,7 +320,7 @@ trait ProcBuilder {
   protected def getEngineHome(shortName: String): String = {
     val homeKey = s"${shortName.toUpperCase}_HOME"
     // 1. get from env, e.g. SPARK_HOME, FLINK_HOME
-    env.get(homeKey)
+    env.get(homeKey).filter(StringUtils.isNotBlank)
       .orElse {
         // 2. get from $KYUUBI_HOME/externals/kyuubi-download/target
         env.get(KYUUBI_HOME).flatMap { p =>