add in the fix from vuejs#7878 to prevent the charAt error

Author: EdBailey

dist/vue.common.js

@@ -1929,7 +1929,7 @@ if (process.env.NODE_ENV !== 'production') {
   var hasHandler = {
     has: function has (target, key) {
       var has = key in target;
-      var isAllowed = allowedGlobals(key) || key.charAt(0) === '_';
+      var isAllowed = allowedGlobals(key) || (typeof key === 'string' && key.charAt(0) === '_');
       if (!has && !isAllowed) {
         warnNonPresent(target, key);
       }

dist/vue.esm.js

@@ -1927,7 +1927,7 @@ if (process.env.NODE_ENV !== 'production') {
   var hasHandler = {
     has: function has (target, key) {
       var has = key in target;
-      var isAllowed = allowedGlobals(key) || key.charAt(0) === '_';
+      var isAllowed = allowedGlobals(key) || (typeof key === 'string' && key.charAt(0) === '_');
       if (!has && !isAllowed) {
         warnNonPresent(target, key);
       }

dist/vue.js

@@ -1929,7 +1929,7 @@ var initProxy;
   var hasHandler = {
     has: function has (target, key) {
       var has = key in target;
-      var isAllowed = allowedGlobals(key) || key.charAt(0) === '_';
+      var isAllowed = allowedGlobals(key) || (typeof key === 'string' && key.charAt(0) === '_');
       if (!has && !isAllowed) {
         warnNonPresent(target, key);
       }

dist/vue.runtime.common.js

@@ -1902,7 +1902,7 @@ if (process.env.NODE_ENV !== 'production') {
   var hasHandler = {
     has: function has (target, key) {
       var has = key in target;
-      var isAllowed = allowedGlobals(key) || key.charAt(0) === '_';
+      var isAllowed = allowedGlobals(key) || (typeof key === 'string' && key.charAt(0) === '_');
       if (!has && !isAllowed) {
         warnNonPresent(target, key);
       }

dist/vue.runtime.esm.js

@@ -1900,7 +1900,7 @@ if (process.env.NODE_ENV !== 'production') {
   var hasHandler = {
     has: function has (target, key) {
       var has = key in target;
-      var isAllowed = allowedGlobals(key) || key.charAt(0) === '_';
+      var isAllowed = allowedGlobals(key) || (typeof key === 'string' && key.charAt(0) === '_');
       if (!has && !isAllowed) {
         warnNonPresent(target, key);
       }

dist/vue.runtime.js

@@ -1902,7 +1902,7 @@ var initProxy;
   var hasHandler = {
     has: function has (target, key) {
       var has = key in target;
-      var isAllowed = allowedGlobals(key) || key.charAt(0) === '_';
+      var isAllowed = allowedGlobals(key) || (typeof key === 'string' && key.charAt(0) === '_');
       if (!has && !isAllowed) {
         warnNonPresent(target, key);
       }

src/core/instance/proxy.js

@@ -45,7 +45,7 @@ if (process.env.NODE_ENV !== 'production') {
   const hasHandler = {
     has (target, key) {
       const has = key in target
-      const isAllowed = allowedGlobals(key) || key.charAt(0) === '_'
+      const isAllowed = allowedGlobals(key) || (typeof key === 'string' && key.charAt(0) === '_')
       if (!has && !isAllowed) {
         warnNonPresent(target, key)
       }