Fix real memory leak

We can't keep the cache around (even though it's tempting) as the next
iteration might change the start time of the planned dive or other
parameters which would make the cached data invalid.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

qt-ui/diveplanner.cpp

@@ -1445,6 +1445,8 @@ void DivePlannerPointsModel::createTemporaryPlan()
 		copy_samples(tempDive, current_dive);
 		copy_events(tempDive, current_dive);
 	}
+	// throw away the cache
+	free(cache);
 #if DEBUG_PLAN
 	dump_plan(&diveplan);
 #endif