Possible null pointer dereference due to return value of devDir.listFiles() in ModuleClassLoader

On lines https://github.com/openmrs/openmrs-core/blob/master/api/src/main/java/org/openmrs/module/ModuleClassLoader.java#L114

And https://github.com/openmrs/openmrs-core/blob/master/api/src/main/java/org/openmrs/module/ModuleClassLoader.java#L209

you will get a null pointer exception if fileList is null. We therefore need to check for null before using it.