tdf#76845: vcl: main thread does not necessarily have SolarMutex

... at least not if VCLXWindowImpl::OnProcessCallbacks drops it and
calls arbitrary event handlers.

So try to make nested SolarMutexReleaser work in that case (although
poorly).

Change-Id: I1e2a1f4d6f42f826692696f7d92d1c3d71291f39

vcl/source/app/svapp.cxx

@@ -394,9 +394,9 @@ void Application::ReAcquireSolarMutex(sal_uLong const nReleased)
 {
     // 0 would mean that events/timers will be handled without locking
     // SolarMutex (racy)
-    assert(nReleased != 0);
+    SAL_WARN_IF(nReleased == 0, "vcl", "SolarMutexReleaser without SolarMutex");
 #ifdef WNT
-    if (ImplGetSVData()->mbDeInit) // do not Yield in DeInitVCL
+    if (nReleased == 0 || ImplGetSVData()->mbDeInit) //do not Yield in DeInitVCL
         AcquireSolarMutex(nReleased);
     else
         ImplYield(false, false, nReleased);