qcap: Fixed a use after free in error path (Coverity).

dlls/qcap/v4l.c

@@ -314,6 +314,7 @@ HRESULT qcap_driver_get_format(const Capture *capBox, AM_MEDIA_TYPE ** mT)
     if (!vi)
     {
         CoTaskMemFree(mT[0]);
+        mT[0] = NULL;
         return E_OUTOFMEMORY;
     }
     mT[0]->majortype = MEDIATYPE_Video;

dlls/qcap/vfwcapture.c

@@ -678,9 +678,10 @@ static HRESULT WINAPI VfwPin_GetMediaType(BasePin *iface, int iPosition, AM_MEDI
         return VFW_S_NO_MORE_ITEMS;
 
     hr = qcap_driver_get_format(This->driver_info, &vfw_pmt);
-    CopyMediaType(pmt, vfw_pmt);
-    DeleteMediaType(vfw_pmt);
-
+    if (SUCCEEDED(hr)) {
+        CopyMediaType(pmt, vfw_pmt);
+        DeleteMediaType(vfw_pmt);
+    }
     return hr;
 }