winecoreaudio.drv: Don't return 0 absolute position if AudioQueue call fails.

Some failures are temporary, for example if the user reconfigures their
audio setup while playing audio. Returning 0 could have bad "going
backward in time" effects which can break audio even after the call
starts to succeed again.

dlls/winecoreaudio.drv/mmdevdrv.c

@@ -688,6 +688,8 @@ static UINT64 get_current_aqbuffer_position(ACImpl *This, int mode)
         if(sc != noErr){
             if(sc != kAudioQueueErr_InvalidRunState)
                 WARN("Unable to get current time: %lx\n", sc);
+            if(mode == BUFPOS_ABSOLUTE)
+                return This->highest_sampletime;
             return 0;
         }