STYLE: simplify short-circuit involving autoPtr (#1775)

- with '&&' conditions, often better to check for non-null autoPtr
  first (it is cheap)

- check as bool instead of valid() method for cleaner code, especially
  when the wrapped item itself has a valid/empty or good.
  Also when handling multiple checks.

  Now
      if (ptr && ptr->valid())
      if (ptr1 || ptr2)

  instead
      if (ptr.valid() && ptr->valid())
      if (ptr1.valid() || ptr2.valid())

applications/utilities/parallelProcessing/redistributePar/redistributePar.C

@@ -1415,9 +1415,9 @@ autoPtr<mapDistributePolyMesh> createReconstructMap
 
     autoPtr<mapDistributePolyMesh> mapPtr;
 
-    if (baseMeshPtr.valid() && baseMeshPtr().nCells())
+    if (baseMeshPtr && baseMeshPtr->nCells())
     {
-        const fvMesh& baseMesh = baseMeshPtr();
+        const fvMesh& baseMesh = *baseMeshPtr;
 
         labelListList cellSubMap(Pstream::nProcs());
         cellSubMap[Pstream::masterNo()] = identity(mesh.nCells());