Add test to ensure "unsatisfied" SATISFY clears trigvalid()

tests/test.cmp

@@ -16578,6 +16578,7 @@ Base: 1991-02-09
 ../tests/test.rem(1611): Expired
 ../tests/test.rem(1612): Expired
 trigvalid = 1; trigdate = 1991-01-14
+trigvalid = 0; trigdate = 0
 Variable hash table statistics:
   Entries: 100143; Buckets: 87719; Non-empty Buckets: 66301
   Maxlen: 5; Minlen: 0; Avglen: 1.142; Stddev: 0.878; Avg nonempty len: 1.510

tests/test.rem

@@ -1619,6 +1619,13 @@ set b trigdate()
 
 REM MSG trigvalid = [a]; trigdate = [b]
 
+# SATISFY clause that's never satisfied...
+REM 14 Jan 1991 SATISFY [$Ty == 2022] MSG I can't get no satisfaction
+set a trigvalid()
+set b trigdate()
+
+REM MSG trigvalid = [a]; trigdate = [b]
+
 # Output expression-node stats
 DEBUG +h