functionObjectList::wordAndDictionary: Added null constructor for pre-7 gcc versions

Resolves bug-report https://bugs.openfoam.org/view.php?id=3479

src/OpenFOAM/db/functionObjects/functionObjectList/wordAndDictionary.C

@@ -27,6 +27,12 @@ License
 
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
+Foam::wordAndDictionary::wordAndDictionary()
+:
+    Tuple2<word, dictionary>()
+{}
+
+
 Foam::wordAndDictionary::wordAndDictionary(Istream& is)
 :
     Tuple2<word, dictionary>()

src/OpenFOAM/db/functionObjects/functionObjectList/wordAndDictionary.H

@@ -89,6 +89,9 @@ public:
         //- Inherit tuple constructors
         using Tuple2<word, dictionary>::Tuple2;
 
+        //- Construct null
+        wordAndDictionary();
+
         //- Construct from Istream
         wordAndDictionary(Istream&);