getBasePath() returns incorrect value for bare stream wrapper path

src/Glob.php

@@ -270,6 +270,11 @@ public static function getBasePath($glob, $flags = 0)
                 return substr($staticPrefix, 0, $pos + 1);
             }
 
+            // If the prefix is a no-path custom stream, that's a valid base path.
+            if ($pos - 2 === strrpos($staticPrefix, '://')) {
+                return $staticPrefix;
+            }
+
             return substr($staticPrefix, 0, $pos);
         }
 

src/Path.php

@@ -46,7 +46,7 @@ public static function isAbsolute(string $path): bool
         }
 
         // UNIX root "/" or "\" (Windows style)
-        if ('/' === $path[0] || '\\' === $path[0]) {
+        if ($path === '' || '/' === $path[0] || '\\' === $path[0]) {
             return true;
         }
 

tests/GlobTest.php

@@ -769,7 +769,7 @@ public function testGetBasePath($glob, $basePath, $flags = 0)
     }
 
     /**
-     * @dataProvider provideBasePaths
+     * @dataProvider provideBasePathsStream
      */
     public function testGetBasePathStream($glob, $basePath)
     {
@@ -793,6 +793,12 @@ public function provideBasePaths()
         );
     }
 
+    public function provideBasePathsStream()
+    {
+        yield from $this->provideBasePaths();
+        yield ['', ''];
+    }
+
     public function testGetBasePathFailsIfNotAbsolute()
     {
         $this->expectException(\InvalidArgumentException::class);