iavcodec/vc1dec: Fix missing {}

Fixes part of Ticket3466
Found-by: Andrey_Karpov / PVS-Studio
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/vc1dec.c

@@ -1913,9 +1913,10 @@ static void vc1_interp_mc(VC1Context *v)
     uvmx = (mx + ((mx & 3) == 3)) >> 1;
     uvmy = (my + ((my & 3) == 3)) >> 1;
     if (v->field_mode) {
-        if (v->cur_field_type != v->ref_field_type[1])
+        if (v->cur_field_type != v->ref_field_type[1]) {
             my   = my   - 2 + 4 * v->cur_field_type;
             uvmy = uvmy - 2 + 4 * v->cur_field_type;
+        }
     }
     if (v->fastuvmc) {
         uvmx = uvmx + ((uvmx < 0) ? -(uvmx & 1) : (uvmx & 1));

tests/ref/fate/vc1_sa10143

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