BUG: externalWallHeatFluxTemperature - set size of qrPrevious_ before

mapping.  Fixes #983

src/TurbulenceModels/compressible/turbulentFluidThermoModels/derivedFvPatchFields/externalWallHeatFluxTemperature/externalWallHeatFluxTemperatureFvPatchScalarField.C

@@ -215,6 +215,7 @@ externalWallHeatFluxTemperatureFvPatchScalarField
 
     if (qrName_ != "none")
     {
+        qrPrevious_.setSize(mapper.size());
         qrPrevious_.map(ptf.qrPrevious_, mapper);
     }
 }