Have secp256k1_ge_set_gej_var initialize all fields.

Previous behaviour would not initialize r->x and r->y values in the case where infinity is passed in.

src/group_impl.h

@@ -100,8 +100,8 @@ static void secp256k1_ge_set_gej(secp256k1_ge *r, secp256k1_gej *a) {
 
 static void secp256k1_ge_set_gej_var(secp256k1_ge *r, secp256k1_gej *a) {
     secp256k1_fe z2, z3;
-    r->infinity = a->infinity;
     if (a->infinity) {
+        secp256k1_ge_set_infinity(r);
         return;
     }
     secp256k1_fe_inv_var(&a->z, &a->z);
@@ -110,8 +110,7 @@ static void secp256k1_ge_set_gej_var(secp256k1_ge *r, secp256k1_gej *a) {
     secp256k1_fe_mul(&a->x, &a->x, &z2);
     secp256k1_fe_mul(&a->y, &a->y, &z3);
     secp256k1_fe_set_int(&a->z, 1);
-    r->x = a->x;
-    r->y = a->y;
+    secp256k1_ge_set_xy(r, &a->x, &a->y);
 }
 
 static void secp256k1_ge_set_all_gej_var(secp256k1_ge *r, const secp256k1_gej *a, size_t len) {