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())

src/functionObjects/forces/forceCoeffs/forceCoeffs.C

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2015-2019 OpenCFD Ltd.
+    Copyright (C) 2015-2020 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -54,7 +54,7 @@ void Foam::functionObjects::forceCoeffs::createFiles()
 {
     // Note: Only possible to create bin files after bins have been initialised
 
-    if (writeToFile() && !coeffFilePtr_.valid())
+    if (writeToFile() && !coeffFilePtr_)
     {
         coeffFilePtr_ = createFile("coefficient");
         writeIntegratedHeader("Coefficients", coeffFilePtr_());

src/functionObjects/forces/forces/forces.C

@@ -58,7 +58,7 @@ void Foam::functionObjects::forces::createFiles()
 {
     // Note: Only possible to create bin files after bins have been initialised
 
-    if (writeToFile() && !forceFilePtr_.valid())
+    if (writeToFile() && !forceFilePtr_)
     {
         forceFilePtr_ = createFile("force");
         writeIntegratedHeader("Force", forceFilePtr_());