Fix base scalar multiplication (#117)

src/groups/curves/short_weierstrass/mod.rs

@@ -559,7 +559,7 @@ where
             .map(|(b, c)| (b.borrow().clone(), *c))
             .unzip();
         let base = bases[0];
-        *self = Self::constant(base).scalar_mul_le(bits.iter())?;
+        *self += Self::constant(base).scalar_mul_le(bits.iter())?;
         Ok(())
     }
 }

src/groups/mod.rs

@@ -134,7 +134,7 @@ pub trait CurveVar<C: CurveGroup, ConstraintF: Field>:
             // else, set self = self;
             result = bit.borrow().select(&self_plus_base, &result)?;
         }
-        *self = result;
+        *self += result;
         Ok(())
     }