[FIX] sap.m.MessageStrip: Warning is no longer logged if type is not defined
[FIX] sap.m.MessageStrip: Warning is no longer logged if type is not defined

Previously if the type of the MessageStrip was 'null' or 'undefined'
a console warning that the type is not supported was logged, however
they are both valid values for resetting a property to its default
state.

BCP: 2180233989
Change-Id: I6c4467b273482db90a6e0cf31b1168c6043c5faf

SAP/openui5,SAP/openui5,SAP/openui5,SAP/openui5