Gradle: Fix getBuiltBy() to work when override.properties does not exist

build.gradle

@@ -33,12 +33,15 @@ String getBuildExtra() {
 }
 
 String getBuiltBy() {
-    def builtBy
+    def builtBy = ""
-    file("override.properties").readLines().findAll({ line ->
+    def overrideProps = file("override.properties")
+    if (overrideProps.exists()) {
+        overrideProps.readLines().findAll({ line ->
             line.contains("build.built-by")
         }).first().eachMatch('.*=(.*)', {
             builtBy = it[1]
         })
+    }
     builtBy
 }