- [x] I have searched the [issues](https://github.com/apache/incubator-dubbo/issues) of this repository and believe that this is not a duplicate.
- [x] I have checked the [FAQ](https://github.com/apache/incubator-dubbo/blob/master/FAQ.md) of this repository and believe that this is not a duplicate.

### Environment

* Dubbo version: 2.7.0
* Operating System version: Mac OS
* Java version: Java 8

### Steps to reproduce this issue

run the following UT

```java
    @Test
    public void testConvertPrimitive() {
        Object result = ClassHelper.convertPrimitive(Integer.class, "");
    }
```


Pls. provide [GitHub address] to reproduce this issue.

### Expected Result

No exception is thrown.

### Actual Result

Following exception is thrown:

```
java.lang.NumberFormatException: For input string: ""

	at java.base/java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
	at java.base/java.lang.Integer.parseInt(Integer.java:662)
	at java.base/java.lang.Integer.valueOf(Integer.java:983)
	at org.apache.dubbo.common.utils.ClassHelper.convertPrimitive(ClassHelper.java:277)
	at org.apache.dubbo.common.utils.ClassHelperTest.testConvertPrimitive(ClassHelperTest.java:125)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
```

### Improvement

1. Throwing exception is expensive, return null if input String is null or ""
2. Add more test cases to this method.
*
     * @param text  text to search and replace in, may be null
     * @param searchString  the String to search for, may be null
     * @param replacement  the String to replace it with, may be null
     * @param max  maximum number of values to replace, or {@code -1} if no maximum
     * @return the text with any replacements processed,
     *  {@code null} if null String input
     */
    public static String replace(final String text, final String searchString, final String replacement, int max) {
        if (isAnyEmpty(text, searchString) || replacement == null || max == 0) {
            return text;
        }
        int start = 0;
        int end = text.indexOf(searchString, start);
        if (end == INDEX_NOT_FOUND) {
            return text;
        }
        final int replLength = searchString.length();
        int increase = replacement.length() - replLength;
        increase = increase < 0 ? 0 : increase;
        increase *= max < 0 ? 16 : max > 64 ? 64 : max;
        final StringBuilder buf = new StringBuilder(text.length() + increase);
        while (end != INDEX_NOT_FOUND) {
            buf.append(text.substring(start, end)).append(replacement);
            start = end + replLength;
            if (--max == 0) {
                break;
            }
            end = text.indexOf(searchString, start);
        }