Add some basic configuration checks

Avoid some segmentation faults caused by ill-formatted configuration files

src/core/receiver/file_configuration.h

@@ -63,6 +63,7 @@ public:
     double property(std::string property_name, double default_value) const override;
     void set_property(std::string property_name, std::string value) override;
     bool is_present(const std::string& property_name) const;
+    bool has_section() const;
 
 private:
     void init();