Fix crash if PAC script retrieval returns a null CFData instance

The documentation for CFURLCreateDataAndPropertiesFromResource()
does not make this clear but from looking at the CFNetwork implementation
and a user stacktrace it appears that this function can return true
but not set the data argument under certain circumstances.

Change-Id: I48034a640d6f47a51cd5883bbafacad4bcbd0415
Task-number: QTBUG-36787
Patch-By: Robert Knight
Reviewed-by: Markus Goetz <markus@woboq.com>
Reviewed-by: Peter Hartmann <phartmann@blackberry.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/src/network/kernel/qnetworkproxy_mac.cpp b/src/network/kernel/qnetworkproxy_mac.cpp
index 6be032ed9b..a1ac349949 100644
--- a/src/network/kernel/qnetworkproxy_mac.cpp
+++ b/src/network/kernel/qnetworkproxy_mac.cpp
@@ -240,7 +240,10 @@ QList<QNetworkProxy> macQueryInternal(const QNetworkProxyQuery &query)
                     qWarning("Unable to get the PAC script at \"%s\" (%s)", qPrintable(pacLocation), cfurlErrorDescription(errorCode));
                     return result;
                 }
-
+                if (!pacData) {
+                    qWarning("\"%s\" returned an empty PAC script", qPrintable(QCFString::toQString(cfPacLocation)));
+                    return result;
+                }
                 QCFType<CFStringRef> pacScript = CFStringCreateFromExternalRepresentation(kCFAllocatorDefault, pacData, kCFStringEncodingISOLatin1);
                 if (!pacScript) {
                     // This should never happen, but the documentation says it may return NULL if there was a problem creating the object.