Fix MM_SIGNAL_UNKNOWN usage
MM_SIGNAL_UNKNOWN was basically 0.0, and that failed helping to detect the values as being unset, as 0.0 may be a good value in some cases. This MR changes the value of MM_SIGNAL_UNKNOWN.
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MM_SIGNAL_UNKNOWN was basically 0.0, and that failed helping to detect the values as being unset, as 0.0 may be a good value in some cases. This MR changes the value of MM_SIGNAL_UNKNOWN.