UI5 MessageStrip - Assertion failed: Method 'class' must be called with exactly one class name

[#1]

Hi, 

I discovered this in a UI5 webapp (not using Fiori Elements) while developing. 

Component: sap.m.MessageStrip
Version affected: 1.143.0+ (until current, 1.144.1)
Version working: 1.142.6
Error: Assertion failed: Method 'class' must be called with exactly one class name
Reproduction: <MessageStrip class="sapUiSmallMargin" text="Test"/>

Even removing the class attribute triggers this failure. There is no MessageStrip in the code, that has more than one CSS class element. There is furthermore no usage of addStyleClass() etc. in the controller logic. 

[M_M · Accepted solution]

Was resolved. Issue was not within the class attribute. It was within the "visible" attribute.

See UI5 MessageStrip Error: Assertion failed: Method '... - SAP Community for details