Fix crash on multi-component bodies. opencog#852

Patterns with multiple components may fail to ground one of
the parts; this is normal and is handled up-stream.

opencog/query/Satisfier.cc

@@ -59,14 +59,19 @@ bool Satisfier::search_finished(bool done)
 	// If there were no variables to be grounded, we have nothing to do.
 	if (not _have_variables) return done;
 
-	// If there was a grounding, then don't don't re-run; we're here
+	// If there was a grounding, then don't re-run; we're here
 	// only to handle the no-groundings case.
 	if (TruthValue::TRUE_TV() == _result) return done;
 
 	// _optionals_present will be set to true if some optional clause
 	// was grounded. Ergo, its not the no-grounding case.
 	if (_optionals_present) return done;
 
+	// Multi-component patterns will not have distinct bodies.
+	// A failure to match one of the components is benign, and is
+	// treated appropriately upstream. Just return.
+	if (nullptr == _pattern_body) return done;
+
 	// Evaluating the pattern body only makes sense if it is sequential
 	// (ordered) -- if the body is an unordered AndLink, or if its a
 	// ChoiceLink, etc, this makes no sense.