Before starting scattering simulation check that refractive index has reasonable magnitude (#715)

Restricts Re(n) to 0.9 .. 1.1. We shall see whether all use cases fall within this range.

This resolves #715 (closed).

Sample/Material/Material.cpp

@@ -81,10 +81,10 @@ void Material::checkRefractiveIndex(double wavelength) const
 {
     const complex_t n = refractiveIndex(wavelength);
     if (n.real() < 0.9 || n.real() > 1.1) {
-	std::stringstream msg;
-	msg << "Refractive index " << n << " at wavelength " << wavelength
-	    << " is too far from 1. Invalid material data?";
-	throw std::runtime_error(msg.str());
+        std::stringstream msg;
+        msg << "Refractive index " << n << " at wavelength " << wavelength
+            << " is too far from 1. Invalid material data?";
+        throw std::runtime_error(msg.str());
     }
 }