Gstreamer: Fix crash when resolution or frame rates are requested

When either resolution or frame rates have been requested when
the camera is in unloaded state, caps might not have some values.

Change-Id: Ie935c62d02e10f762957ecd9f89255ad0e8fbd0b
Reviewed-by: Christian Stromme <christian.stromme@qt.io>

src/plugins/gstreamer/camerabin/camerabinsession.cpp

@@ -1294,6 +1294,9 @@ QList< QPair<int,int> > CameraBinSession::supportedFrameRates(const QSize &frame
         GstStructure *structure = gst_caps_get_structure(caps, i);
         gst_structure_set_name(structure, "video/x-raw");
         const GValue *oldRate = gst_structure_get_value(structure, "framerate");
+        if (!oldRate)
+            continue;
+
         GValue rate;
         memset(&rate, 0, sizeof(rate));
         g_value_init(&rate, G_VALUE_TYPE(oldRate));
@@ -1310,6 +1313,9 @@ QList< QPair<int,int> > CameraBinSession::supportedFrameRates(const QSize &frame
     for (uint i=0; i<gst_caps_get_size(caps); i++) {
         GstStructure *structure = gst_caps_get_structure(caps, i);
         const GValue *rateValue = gst_structure_get_value(structure, "framerate");
+        if (!rateValue)
+            continue;
+
         readValue(rateValue, &res, continuous);
     }
 
@@ -1401,6 +1407,9 @@ QList<QSize> CameraBinSession::supportedResolutions(QPair<int,int> rate,
         gst_structure_set_name(structure, "video/x-raw");
         const GValue *oldW = gst_structure_get_value(structure, "width");
         const GValue *oldH = gst_structure_get_value(structure, "height");
+        if (!oldW || !oldH)
+            continue;
+
         GValue w;
         memset(&w, 0, sizeof(GValue));
         GValue h;
@@ -1425,6 +1434,8 @@ QList<QSize> CameraBinSession::supportedResolutions(QPair<int,int> rate,
         GstStructure *structure = gst_caps_get_structure(caps, i);
         const GValue *wValue = gst_structure_get_value(structure, "width");
         const GValue *hValue = gst_structure_get_value(structure, "height");
+        if (!wValue || !hValue)
+            continue;
 
         QPair<int,int> wRange = valueRange(wValue, &isContinuous);
         QPair<int,int> hRange = valueRange(hValue, &isContinuous);