Default Scope does not work as expected

resolves issue #1092

Author: datapp

src/Grant/AbstractGrant.php

@@ -316,7 +316,7 @@ public function validateScopes($scopes, $redirectUri = null)
     private function convertScopesQueryStringToArray($scopes)
     {
         return \array_filter(\explode(self::SCOPE_DELIMITER_STRING, \trim($scopes)), function ($scope) {
-            return !empty($scope);
+            return $scope !== '';
         });
     }
 

tests/Grant/AbstractGrantTest.php

@@ -431,13 +431,13 @@ public function testValidateScopes()
     {
         $scope = new ScopeEntity();
         $scopeRepositoryMock = $this->getMockBuilder(ScopeRepositoryInterface::class)->getMock();
-        $scopeRepositoryMock->method('getScopeEntityByIdentifier')->willReturn($scope);
+        $scopeRepositoryMock->expects($this->exactly(3))->method('getScopeEntityByIdentifier')->willReturn($scope);
 
         /** @var AbstractGrant $grantMock */
         $grantMock = $this->getMockForAbstractClass(AbstractGrant::class);
         $grantMock->setScopeRepository($scopeRepositoryMock);
 
-        $this->assertEquals([$scope], $grantMock->validateScopes('basic   '));
+        $this->assertEquals([$scope, $scope, $scope], $grantMock->validateScopes('basic  test 0    '));
     }
 
     public function testValidateScopesBadScope()