MULE-7256: WS consumer throws NullPointerException when defining an empty security element
MULE-7256: WS consumer throws NullPointerException when defining an empty security element

Changed WSSecurity so that the strategy list can never be null
Merge pull request #307 from mulesoft/MULE-7256

MULE-7256: WS consumer throws NullPointerException when defining an empty security element