STYLE: check autoPtr as plain bool instead of valid()

- cleaner code, more similarity with unique_ptr

  Now
      if (ptr)
      if (!ptr)

  instead
      if (ptr.valid())
      if (!ptr.valid())

src/sampling/sampledSet/patchSeed/patchSeedSet.C

@@ -81,11 +81,11 @@ void Foam::patchSeedSet::calcSamples
     }
 
 
-    if (!rndGenPtr_.valid())
+    if (!rndGenPtr_)
     {
         rndGenPtr_.reset(new Random(0));
     }
-    Random& rndGen = rndGenPtr_();
+    Random& rndGen = *rndGenPtr_;
 
 
     if (selectedLocations_.size())