修复 java.lang.NullPointerException

Attempt to invoke virtual method 'void java.lang.Thread.interrupt()' on a null object reference

autojs/src/main/java/com/stardust/autojs/core/util/Shell.java

@@ -304,7 +304,9 @@ public class Shell extends AbstractShell {
             super.finish();
             if (!mShouldReadOutput)
                 return;
-            mReadingThread.interrupt();
+            if(mReadingThread != null){
+                mReadingThread.interrupt();
+            }
             try {
                 mBufferedReader.close();
                 mOutputStream.close();