SET_VERSION should change password length

close https://github.com/lesspass/lesspass/issues/148

src/store/mutations.js

@@ -42,11 +42,9 @@ export default {
         state.baseURL = baseURL;
     },
     [types.SET_VERSION](state, {version}){
-        if (state.password === null) {
-            state.password = {version};
-        } else {
-            state.password.version = version;
-        }
+        const length = version === 1 ? 12 : 16;
+        state.password.version = version;
+        state.password.length = length;
     },
     [types.LOAD_PASSWORD_FIRST_TIME](state){
         const tenMinutesAgo = new Date().getTime() - 60 * 1000;

test/store.mutations.js

@@ -150,13 +150,22 @@ test('SET_VERSION', t => {
     t.is(state.password.version, 1);
 });
 
-test('SET_VERSION password null', t => {
+test('SET_VERSION 1 should modify length to 12', t => {
     const SET_VERSION = mutations[types.SET_VERSION];
     const state = {
-        password: null,
+        password: {length: 16, version: 2},
+    };
+    SET_VERSION(state, {version: 1});
+    t.is(state.password.length, 12);
+});
+
+test('SET_VERSION 2 should modify length to 16', t => {
+    const SET_VERSION = mutations[types.SET_VERSION];
+    const state = {
+        password: {length: 12, version: 1},
     };
     SET_VERSION(state, {version: 2});
-    t.is(state.password.version, 2);
+    t.is(state.password.length, 16);
 });
 
 test('LOAD_PASSWORD_FIRST_TIME 30 seconds after last use', t => {