Internals: Fix -DLEAK_CHECKS failing due to visitor destructor being too late.

src/V3CoverageJoin.cpp

@@ -134,6 +134,8 @@ public:
 
 void V3CoverageJoin::coverageJoin(AstNetlist* rootp) {
     UINFO(2,__FUNCTION__<<": "<<endl);
-    CoverageJoinVisitor visitor (rootp);
+    {
+        CoverageJoinVisitor visitor (rootp);
+    }  // Destruct before checking
     V3Global::dumpCheckGlobalTree("coveragejoin", 0, v3Global.opt.dumpTreeLevel(__FILE__) >= 3);
 }