Clear all ssrc attributes in reciprocated sdp, as they are individual.

src/description.cpp

@@ -690,9 +690,9 @@ Description::Media Description::Media::reciprocate() const {
 		break;
 	}
 
-	// Clear all ssrc attributes as them are individual
-	auto it = mAttributes.begin();
-	while (it != mAttributes.end()) {
+	// Clear all ssrc attributes as they are individual
+	auto it = reciprocated.mAttributes.begin();
+	while (it != reciprocated.mAttributes.end()) {
 		if (match_prefix(*it, "ssrc:"))
 			it = reciprocated.mAttributes.erase(it);
 		else