Prep env for 4.2

src/main/java/com/sheepit/client/Job.java

@@ -196,6 +196,7 @@ import java.util.regex.Pattern;
 		//make sure the system doesn´t interfere with the blender runtime, and that blender doesn´t attempt to load external libraries/scripts.
 		new_env.put("BLENDER_USER_RESOURCES", "");
 		new_env.put("BLENDER_USER_CONFIG", "");
+		new_env.put("BLENDER_USER_EXTENSIONS", "");
 		new_env.put("BLENDER_USER_SCRIPTS", "");
 		new_env.put("BLENDER_USER_DATAFILES", "");