default filepath is now an empty string, SetupWriter will throw an error if path not set (#1133)

Co-authored-by: Dhanya Thattil <dhanya.thattil@psi.ch>

slsReceiverSoftware/src/Implementation.cpp

@@ -919,7 +919,12 @@ void Implementation::CreateUDPSockets() {
 }
 
 void Implementation::SetupWriter() {
+    
     try {
+        //check if filePath empty and throw error
+        if(filePath.empty()){
+            throw ReceiverError("File path cannot be empty");
+        }
         // check if folder exists and throw if it cant create
         mkdir_p(filePath);
         // create first files