check for empty word/expression in keyType and wordRe IO

src/OpenFOAM/primitives/Scalar/Scalar.C

src/OpenFOAM/primitives/bools/Switch/SwitchIO.C

src/OpenFOAM/primitives/ints/int/intIO.C

src/OpenFOAM/primitives/ints/long/longIO.C

src/OpenFOAM/primitives/ints/uint/uintIO.C

src/OpenFOAM/primitives/ints/ulong/ulongIO.C

src/OpenFOAM/primitives/strings/keyType/keyTypeIO.C

src/OpenFOAM/primitives/strings/string/stringIO.C

src/OpenFOAM/primitives/strings/word/wordIO.C

src/OpenFOAM/primitives/strings/wordRe/wordReIO.C