fix set null crash bug

README-zh.md

@@ -86,6 +86,7 @@ compile 'com.github.fingdo:stateLayout:1.0.1'
 ```
 
 ### 代码提前设置图标和文字
+#### 如果你设置了一个`null`数据的时候，将使用上一次设置的提示语。空字符串可以正常显示为空，即只显示一个提示图片。
 ``` java
 //type为StateLayout的固定Type变量
 public static final int ERROR = 1;

README.md

@@ -7,7 +7,7 @@
 
 ## Dependently
 - one step
-add to your project `build.gradle`
+  add to your project `build.gradle`
 
 ``` base
 allprojects {
@@ -17,7 +17,7 @@ allprojects {
 	}
 }
 
-``` 
+```
 - second step
 
 ``` base
@@ -90,6 +90,7 @@ Usage is consistent with `ScrollView`, allowing only one root layout
 ```
 
 ### Code set icon and text (show before)
+#### if you set `null`,will use last time tip text.set "" can show,only show tip image.
 ``` java
 //StateLayout Constants Type
 public static final int ERROR = 1;

library/src/main/java/com/fingdo/statelayout/StateLayout.java

@@ -2,6 +2,7 @@
 
 import android.content.Context;
 import android.graphics.drawable.Drawable;
+import android.text.TextUtils;
 import android.util.AttributeSet;
 import android.view.LayoutInflater;
 import android.view.View;
@@ -492,6 +493,9 @@ public void showCustomView(View view) {
      * @param text 文字
      */
     public void setTipText(int type, String text) {
+        if (text == null) { //text is null
+            return;
+        }
         switch (type) {
             case ERROR:
                 ((ErrorViewHolder) errorView.getTag()).tvTip.setText(text);