msi: Fixed MsiGetFileHashW for empty files.

dlls/msi/msi.c

@@ -4014,6 +4014,8 @@ UINT WINAPI MsiGetFileHashW( LPCWSTR szFilePath, DWORD dwOptions,
     }
     length = GetFileSize( handle, NULL );
 
+    if (length)
+    {
         mapping = CreateFileMappingW( handle, NULL, PAGE_READONLY, 0, 0, NULL );
         if (mapping)
         {
@@ -4032,6 +4034,14 @@ UINT WINAPI MsiGetFileHashW( LPCWSTR szFilePath, DWORD dwOptions,
             }
             CloseHandle( mapping );
         }
+    }
+    else
+    {
+        /* Empty file -> set hash to 0 */
+        memset( pHash->dwData, 0, sizeof pHash->dwData );
+        r = ERROR_SUCCESS;
+    }
+
     CloseHandle( handle );
 
     return r;

dlls/msi/tests/msi.c

@@ -417,6 +417,12 @@ static const struct
     MSIFILEHASHINFO hash;
 } hash_data[] =
 {
+    { "", 0,
+      { HASHSIZE,
+        { 0, 0, 0, 0 },
+      },
+    },
+
     { "abc", 0,
       { HASHSIZE,
         { 0x98500190, 0xb04fd23c, 0x7d3f96d6, 0x727fe128 },