Fix incorrect exception types

include/util.h

@@ -10,7 +10,7 @@ inline std::string read_setting_default(const std::string &name, std::istream &i
 {
 	try {
 		return read_setting(name, is);
-	} catch(std::runtime_error e) {
+	} catch(std::runtime_error &e) {
 		return def;
 	}
 }

mapper.cpp

@@ -221,7 +221,7 @@ int main(int argc, char *argv[])
 		generator.parseColorsFile(colors);
 		generator.generate(input, output);
 
-	} catch(std::runtime_error e) {
+	} catch(std::runtime_error &e) {
 		std::cerr << "Exception: " << e.what() << std::endl;
 		return 1;
 	}