poll: don't call WSAWaitForMultipleEvents with no events
poll: don't call WSAWaitForMultipleEvents with no events

Fixes error caught by Microsoft Application Verifier.

collects/gstreamer,collects/gstreamer,ensonic/gstreamer,mparis/gstreamer,ylatuya/gstreamer,StreamUtils/gstreamer,lovebug356/gstreamer,lovebug356/gstreamer,surround-io/gstreamer,ylatuya/gstreamer,Lachann/gstreamer,cfoch/gstreamer,collects/gstreamer,jpxiong/gstreamer,surround-io/gstreamer,cfoch/gstreamer,Distrotech/gstreamer,Lachann/gstreamer,krieger-od/gstreamer,ylatuya/gstreamer,cfoch/gstreamer,krichter722/gstreamer,shelsonjava/gstreamer,krieger-od/gstreamer,Distrotech/gstreamer,krichter722/gstreamer,justinjoy/gstreamer,StreamUtils/gstreamer,centricular/gstreamer,StreamUtils/gstreamer,jpxiong/gstreamer,lovebug356/gstreamer,mparis/gstreamer,StreamUtils/gstreamer,krichter722/gstreamer,krieger-od/gstreamer,drothlis/gstreamer,mparis/gstreamer,ahmedammar/platform_external_gst_gstreamer,cablelabs/gstreamer,lovebug356/gstreamer,magcius/gstreamer,jpakkane/gstreamer,lubosz/gstreamer,ensonic/gstreamer,lubosz/gstreamer,ahmedammar/platform_external_gst_gstreamer,cablelabs/gstreamer,magcius/gstreamer,krichter722/gstreamer,cablelabs/gstreamer,centricular/gstreamer,collects/gstreamer,Distrotech/gstreamer,lubosz/gstreamer,cfoch/gstreamer,Lachann/gstreamer,ylatuya/gstreamer,jpxiong/gstreamer,ahmedammar/platform_external_gst_gstreamer,Distrotech/gstreamer,shelsonjava/gstreamer,centricular/gstreamer,collects/gstreamer,justinjoy/gstreamer,shelsonjava/gstreamer,drothlis/gstreamer,jpakkane/gstreamer,Distrotech/gstreamer,jpakkane/gstreamer,krichter722/gstreamer,surround-io/gstreamer,centricular/gstreamer,jpakkane/gstreamer,centricular/gstreamer,cablelabs/gstreamer,krieger-od/gstreamer,ensonic/gstreamer,drothlis/gstreamer,magcius/gstreamer,Lachann/gstreamer,cablelabs/gstreamer,Lachann/gstreamer,justinjoy/gstreamer,shelsonjava/gstreamer,ensonic/gstreamer,krieger-od/gstreamer,mparis/gstreamer,justinjoy/gstreamer,lubosz/gstreamer,lubosz/gstreamer,drothlis/gstreamer,surround-io/gstreamer,surround-io/gstreamer,shelsonjava/gstreamer,jpxiong/gstreamer,lovebug356/gstreamer,mparis/gstreamer,jpakkane/gstreamer,ylatuya/gstreamer,ensonic/gstreamer,ahmedammar/platform_external_gst_gstreamer,ahmedammar/platform_external_gst_gstreamer,magcius/gstreamer,magcius/gstreamer,StreamUtils/gstreamer,jpxiong/gstreamer,cfoch/gstreamer,drothlis/gstreamer,justinjoy/gstreamer