Handle the invalid warped model error

Handled the invalid warped model error in the decoder.

BUG=aomedia:610

Change-Id: I8a67a4f6c6fe4dd6c2a71fdef432b3f689e9efcb

av1/decoder/decodemv.c

diff --git a/av1/decoder/decodemv.c b/av1/decoder/decodemv.c
index 10fefa6..d556784 100644
--- a/av1/decoder/decodemv.c
+++ b/av1/decoder/decodemv.c
@@ -2549,7 +2549,7 @@
       if (find_projection(mbmi->num_proj_ref[0], pts, pts_inref, bsize,
                           mbmi->mv[0].as_mv.row, mbmi->mv[0].as_mv.col,
                           &mbmi->wm_params[0], mi_row, mi_col)) {
-        assert(0 && "Invalid Warped Model.");
+        aom_internal_error(&cm->error, AOM_CODEC_ERROR, "Invalid Warped Model");
       }
     }
 #endif  // CONFIG_WARPED_MOTION