Fix issue qii#270: Cannot invoke method minus() on null object

build.gradle

@@ -4,7 +4,7 @@ buildscript {
         maven { url 'http://download.crashlytics.com/maven' }
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:0.13.2'
+        classpath 'com.android.tools.build:gradle:1.1.1'
         classpath 'com.crashlytics.tools.gradle:crashlytics-gradle:1.+'
     }
 }
@@ -33,7 +33,7 @@ android {
         applicationId "org.qii.weiciyuan"
         minSdkVersion 17
         targetSdkVersion 21
-        versionCode - 1
+        versionCode 1
         versionName null
     }
 
@@ -106,15 +106,15 @@ android {
             resValue "string", "weiciyuanOfficalWeiboName",
                     "org.qii.weiciyuan" + getApplicationIdSuffix() + ".mention://@四次元App"
             debuggable true
-            runProguard false
+            minifyEnabled false
             signingConfig signingConfigs.debug
         }
         release {
             resValue "string", "applicationId", "org.qii.weiciyuan"
             resValue "string", "weiciyuanOfficalWeiboName",
                     "org.qii.weiciyuan" + ".mention://@四次元App"
             debuggable false
-            runProguard false
+            minifyEnabled false
             signingConfig signingConfigs.release
         }