fix error handling in Camera::getDescription()

uvoscam.h

@@ -39,6 +39,8 @@ public:
 	
 	class Description
 	{
+	private:
+		size_t hash = 0;
 	public:
 		std::string vendor;
 		std::string serial;
@@ -47,7 +49,9 @@ public:
 		
 		size_t getHash() const
 		{
-			return std::hash<std::string>{}(vendor + serial + id + model);
+			//if(hash == 0)
+				return /*hash =*/ std::hash<std::string>{}(vendor + serial + id + model);
+			//return hash;
 		}
 		
 		bool operator==(const Description& in) const
@@ -83,6 +87,8 @@ private:
 	ArvStream* aStream_ = nullptr;
 	ArvCamera* aCamera_ = nullptr;
 	
+	Description* description = nullptr;
+	
 	unsigned int width_;
 	unsigned int height_;
 	int64_t format = -1;