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.h

@@ -314,7 +314,7 @@ class Implementation : private virtual slsDetectorDefs {
 
     // file parameters
     fileFormat fileFormatType{BINARY};
-    std::string filePath{"/"};
+    std::string filePath{};
     std::string fileName{"run"};
     uint64_t fileIndex{0};
     bool fileWriteEnable{false};