Fix memory leaks in qt/guiutil.cpp

on macOS:
listSnapshot was leaking in findStartupItemInList()
bitcoinAppUrl was leaking in [Get|Set]StartOnSystemStartup()

src/qt/guiutil.cpp

@@ -780,8 +780,12 @@ bool SetStartOnSystemStartup(bool fAutoStart)
 LSSharedFileListItemRef findStartupItemInList(LSSharedFileListRef list, CFURLRef findUrl);
 LSSharedFileListItemRef findStartupItemInList(LSSharedFileListRef list, CFURLRef findUrl)
 {
-    // loop through the list of startup items and try to find the bitcoin app
     CFArrayRef listSnapshot = LSSharedFileListCopySnapshot(list, nullptr);
+    if (listSnapshot == nullptr) {
+        return nullptr;
+    }
+    
+    // loop through the list of startup items and try to find the bitcoin app
     for(int i = 0; i < CFArrayGetCount(listSnapshot); i++) {
         LSSharedFileListItemRef item = (LSSharedFileListItemRef)CFArrayGetValueAtIndex(listSnapshot, i);
         UInt32 resolutionFlags = kLSSharedFileListNoUserInteraction | kLSSharedFileListDoNotMountVolumes;
@@ -798,29 +802,42 @@ LSSharedFileListItemRef findStartupItemInList(LSSharedFileListRef list, CFURLRef
         LSSharedFileListItemResolve(item, resolutionFlags, &currentItemURL, nullptr);
 #endif
 
-        if(currentItemURL && CFEqual(currentItemURL, findUrl)) {
+        if(currentItemURL) {
+            if (CFEqual(currentItemURL, findUrl)) {
                 // found
+                CFRelease(listSnapshot);
                 CFRelease(currentItemURL);
                 return item;
             }
-        if(currentItemURL) {
             CFRelease(currentItemURL);
         }
     }
+    
+    CFRelease(listSnapshot);
     return nullptr;
 }
 
 bool GetStartOnSystemStartup()
 {
     CFURLRef bitcoinAppUrl = CFBundleCopyBundleURL(CFBundleGetMainBundle());
+    if (bitcoinAppUrl == nullptr) {
+        return false;
+    }
+    
     LSSharedFileListRef loginItems = LSSharedFileListCreate(nullptr, kLSSharedFileListSessionLoginItems, nullptr);
     LSSharedFileListItemRef foundItem = findStartupItemInList(loginItems, bitcoinAppUrl);
+
+    CFRelease(bitcoinAppUrl);
     return !!foundItem; // return boolified object
 }
 
 bool SetStartOnSystemStartup(bool fAutoStart)
 {
     CFURLRef bitcoinAppUrl = CFBundleCopyBundleURL(CFBundleGetMainBundle());
+    if (bitcoinAppUrl == nullptr) {
+        return false;
+    }
+    
     LSSharedFileListRef loginItems = LSSharedFileListCreate(nullptr, kLSSharedFileListSessionLoginItems, nullptr);
     LSSharedFileListItemRef foundItem = findStartupItemInList(loginItems, bitcoinAppUrl);
 
@@ -832,6 +849,8 @@ bool SetStartOnSystemStartup(bool fAutoStart)
         // remove item
         LSSharedFileListItemRemove(loginItems, foundItem);
     }
+    
+    CFRelease(bitcoinAppUrl);
     return true;
 }
 #pragma GCC diagnostic pop