app-inspector is not producing source for android devices running API version 18-21

[qichuan]

app-inspector version: 2.0.8
macaca-doctor version: 2.0.3

Node.js checklist:

node env: /usr/local/bin/node
node version: v6.11.3

iOS checklist:

Xcode Command Line Tools is ready, version: 2349.
xcodebuild version: 9.0
iproxy[usbmuxd] is installed at: /usr/local/bin/iproxy
ios_webkit_debug_proxy is installed at: /usr/local/bin/ios_webkit_debug_proxy
carthage is installed, version: 0.25.0

Android checklist:

JAVA version is 1.8.0_144
JAVA_HOME is set to /Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home
ANDROID_HOME is set to /Users/sean/Library/Android/sdk
Platforms is set to /Users/sean/Library/Android/sdk/platforms/android-26
ADB tool is set to /Users/sean/Library/Android/sdk/platform-tools/adb
gradle is installed, version: 4.2

Installed driver list:

android: 2.0.40
chrome: 1.0.6
ios: 2.0.27

Finding:
The content of generated android.json file is "0"

[qichuan]

Fixed in macacajs/app-inspector#148