Fix Appium crash when fails getting source page in Android

If you use xpath to find an element and the app is still loading, the pull command fails, the error is not catched and Appium dies.

info: [BOOTSTRAP] [debug] Got command action: dumpWindowHierarchy
info: [BOOTSTRAP] [info] Returning result: {"value":true,"status":0}
debug: transferPageSourceXML command: "D:\android-sdk\platform-tools\adb.exe" -s emulator-5554 pull /data/local/tmp/dump.xml "C:\Users\username\AppData\Local\Temp\114322-11496-8ey6c4.xml"
warn: remote object '/data/local/tmp/dump.xml' does not exist
error: uncaughtException: ENOENT, no such file or directory 'C:\Users\username\AppData\Local\Temp\114322-11496-8ey6c4.xml' [...]