Check remoteSiteDir property is available before using in build file.

build.gradle

@@ -88,7 +88,11 @@ task login {
 }
 
 // Define remoteSiteDir and sshHost in gradle.properties
-def remoteDocsDir="$remoteSiteDir/docs/3.1.x"
+def remoteDocsDir = null
+
+if (hasProperty('remoteSiteDir')) {
+    remoteDocsDir="$remoteSiteDir/docs/3.1.x"
+}
 
 task uploadApidocs(dependsOn: login) << {
     ant {