Fix last Liquidity Provider withdrawal:

Due to the rounding, LPTokenBalance of the last
Liquidity Provider (LP), might not match this LP's
trustline balance. This fix sets LPTokenBalance on
last LP withdrawal to this LP's LPToken trustline
balance.

src/test/jtx/impl/AMMTest.cpp

@@ -137,10 +137,15 @@ AMMTestBase::testAMM(
         else if (asset2.native())
             fund(env, gw, {alice, carol}, toFund2, {toFund1}, Fund::All);
 
-        AMM ammAlice(env, alice, asset1, asset2, false, tfee);
-        BEAST_EXPECT(
-            ammAlice.expectBalances(asset1, asset2, ammAlice.tokens()));
-        cb(ammAlice, env);
+        AMM ammAlice(
+            env,
+            alice,
+            asset1,
+            asset2,
+            CreateArg{.log = false, .tfee = tfee, .err = ter});
+        if (BEAST_EXPECT(
+                ammAlice.expectBalances(asset1, asset2, ammAlice.tokens())))
+            cb(ammAlice, env);
     }
 }