fix ($http): throw error when string URL is provided

docs/content/error/$http/badreq.ngdoc

@@ -0,0 +1,10 @@
+@ngdoc error
+@name $http:badreq
+@fullName Bad Request Configuration
+@description
+
+This error occurs when the request configuration parameter passed to the {@link ng.$http `$http`} service is not an object.  `$http` expects a single parameter, the request configuration object, but received a parameter that was not an object.  The error message should provide additional context such as the actual value of the parameter that was received.  If you passed a string parameter, perhaps you meant to call one of the shorthand methods on `$http` such as `$http.get(…)`, etc.
+
+To resolve this error, make sure you pass a valid request configuration object to `$http`.
+
+For more information, see the {@link ng.$http `$http`} service API documentation.

src/ng/http.js

@@ -743,6 +743,10 @@ function $HttpProvider() {
       };
       var headers = mergeHeaders(requestConfig);
 
+      if (!angular.isObject(requestConfig)) {
+        throw minErr('$http')('badreq', 'Http request configuration must be an object.  Received: {0}', requestConfig);
+      }
+
       extend(config, requestConfig);
       config.headers = headers;
       config.method = uppercase(config.method);

test/ng/httpSpec.js

@@ -285,6 +285,12 @@ describe('$http', function() {
       $http = $h;
     }]));
 
+    it('should throw error if the request configuration is not an object', inject(function($httpBackend, $http) {
+      expect(function() {
+          $http('/url');
+      }).toThrowMinErr('$http','badreq', 'Http request configuration must be an object.  Received: /url');
+    }));
+
     it('should send GET requests if no method specified', inject(function($httpBackend, $http) {
       $httpBackend.expect('GET', '/url').respond('');
       $http({url: '/url'});