SfxInfoBarContainerWindow: pInfoBar can be 0 here

	0x00007ffff0b36bf0 in OutputDevice::disposeOnce (this=0x0) at /git/libreoffice/master/vcl/source/outdev/outdev.cxx:193
	193         if ( mbDisposed )
	(gdb) up
	#1  0x00007ffff3c3d651 in SfxInfoBarContainerWindow::removeInfoBar (this=0x1f05b30, pInfoBar=0x0) at /git/libreoffice/master/sfx2/source/dialog/infobar.cxx:294
	294         pInfoBar->disposeOnce();

Change-Id: I7b5dfddea98d8ab3d4f7db3ef53660f91e5ad80b

sfx2/source/dialog/infobar.cxx

@@ -291,7 +291,8 @@ void SfxInfoBarContainerWindow::removeInfoBar(SfxInfoBarWindow* pInfoBar)
             break;
         }
     }
-    pInfoBar->disposeOnce();
+    if (pInfoBar)
+        pInfoBar->disposeOnce();
 
     long nY = 0;
     for (auto it = m_pInfoBars.begin(); it != m_pInfoBars.end(); ++it)