Crash in SurfaceTextureTarget filter open

If the filter graph in an app closes out, the SurfaceTextureTarget
filter was losing the reference to the original surfacetexture, and the
app would re-start the graph without setting the surfacetexture again,
thus leading to a crash in registering a surface from surfacetexture.

Typical scenarios is start/stop immediately in camera effects recording.

Fix part of b/6651352
Fix part of b/6655597

Change-Id: Ib2bae7e886784e91b3a886f7ccd439ff190feb22