Micro-tweak for MacOS reslience (#1023)

We had a user who had a ~/L/AS/Surge dir with no contents
unable to start the app even after the installer had run.
So rather than just test if the local directory exists,
also test if it contains a configuration.xml as a proxy
for a properl local install on macOS

Closes #863

src/common/SurgeStorage.cpp

@@ -145,13 +145,16 @@ SurgeStorage::SurgeStorage(std::string suppliedDataPath)
        FSRefMakePath(&foundRef, (UInt8*)path, 1024);
        datapath = path;
        datapath += "/Surge/";
-
+
+       auto cxmlpath = datapath + "configuration.xml";
        // check if the directory exist in the user domain (if it doesn't, fall back to the local domain)
-       CFStringRef testpathCF = CFStringCreateWithCString(0, datapath.c_str(), kCFStringEncodingUTF8);
+       // See #863 where I chaned this to dir exists and contains config
+       CFStringRef testpathCF = CFStringCreateWithCString(0, cxmlpath.c_str(), kCFStringEncodingUTF8);
        CFURLRef testCat = CFURLCreateWithFileSystemPath(0, testpathCF, kCFURLPOSIXPathStyle, true);
        CFRelease(testpathCF);
        FSRef myfsRef;
        Boolean works = CFURLGetFSRef(testCat, &myfsRef);
+
        CFRelease(testCat); // don't need it anymore?!?
        if (!works)
        {