rdopt: clear maybe-uninitialized variable warning

av1/encoder/rdopt.c:9533 ‘zeromv[1].as_int’ may be used
uninitialized in this function [-Wmaybe-uninitialized]
this was spurious given the logic in the if

Change-Id: I8ddfe7e46d1bf5593cc8624f05c9f181243a87d4

av1/encoder/rdopt.c

@@ -9454,10 +9454,10 @@ PALETTE_EXIT:
 #endif  // CONFIG_REF_MV
 #if CONFIG_GLOBAL_MOTION
     zeromv[0].as_int = cm->global_motion[refs[0]].motion_params.wmmat[0].as_int;
-    if (comp_pred_mode) {
-      zeromv[1].as_int =
-          cm->global_motion[refs[1]].motion_params.wmmat[0].as_int;
-    }
+    zeromv[1].as_int =
+        comp_pred_mode
+            ? cm->global_motion[refs[1]].motion_params.wmmat[0].as_int
+            : 0;
 #else
     zeromv[0].as_int = 0;
     zeromv[1].as_int = 0;