Guard against render time query failing

glGetQuery can fail (for example because of a context loss) in this
case the buffer stays unmodified. In this case this is zero resulting
in GLRenderTimeQuery::result() returning a negative value. Down the
line this leads to a negative duration in the RenderJournal and
RenderLoopPrivate::scheduleRepaint starting a timer with an amount
of milliseconds bigger than what an int can hold. This will not
actually start a timer but QTimer::isActive returns true resulting
in no futher repaints being scheduled.
BUG: 475605
FIXED-IN: 6.0

src/opengl/glrendertimequery.cpp

@@ -56,6 +56,9 @@ std::chrono::nanoseconds GLRenderTimeQuery::result()
     if (m_query) {
         uint64_t nanos = 0;
         glGetQueryObjectui64v(m_query, GL_QUERY_RESULT, &nanos);
+        if (nanos == 0) {
+            return std::chrono::nanoseconds::zero();
+        }
         return std::chrono::nanoseconds(nanos) - m_cpuStart;
     } else {
         return m_cpuEnd - m_cpuStart;