"Constant" blocks that have the "sampled constant" option unchecked will generate a Matlab error as follows:
How can I work around this issue?
It appears that the simulation and generation of the design will still function without issue.
To work around this issue you can do one of the following:
1) Select to enable the "Sampled Constant" feature in the Constant block.
2) Check the "Inline Parameters" checkbox for simulation.
From the Simulation menu select Model Configuration Parameters -> Optimization -> Signals and Parameters
Check the Inline Parameters checkbox.
Please review this Matlab Answer Record for further information on Sample Times in Simulink.