ImageMagick 7.0.8-35 has a memory leak in magick/xwindow.c, related to XCreateImage.
### Prerequisites

- [x] I have written a descriptive issue title
- [x] I have verified that I am using the latest version of ImageMagick
- [x] I have searched [open](https://github.com/ImageMagick/ImageMagick/issues) and [closed](https://github.com/ImageMagick/ImageMagick/issues?q=is%3Aissue+is%3Aclosed) issues to ensure it has not already been reported

### Description
```
=================================================================
==15742==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 136 byte(s) in 1 object(s) allocated from:
    #0 0x7fadbfd0c79a in __interceptor_calloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x9879a)
    #1 0x7fadbcb0e220 in XCreateImage (/usr/lib/x86_64-linux-gnu/libX11.so.6+0x27220)

Indirect leak of 48000 byte(s) in 1 object(s) allocated from:
    #0 0x7fadbfd0c602 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x98602)
    #1 0x508cf3 in XMakeImage MagickCore/xwindow.c:5733
    #2 0x82940c in XConfigureImage MagickCore/display.c:4449
    #3 0x85e6bd in XDisplayImage MagickCore/display.c:15069
    #4 0x81b445 in DisplayImages MagickCore/display.c:1705
    #5 0x77475f in WriteXImage coders/x.c:202
    #6 0x808fb6 in WriteImage MagickCore/constitute.c:1226
    #7 0x8097ea in WriteImages MagickCore/constitute.c:1376
    #8 0xbb0499 in ConvertImageCommand MagickWand/convert.c:3305
    #9 0xc9c5ea in MagickCommandGenesis MagickWand/mogrify.c:184
    #10 0x40e941 in MagickMain utilities/magick.c:149
    #11 0x40eb22 in main utilities/magick.c:180
    #12 0x7fadbbffc82f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)

SUMMARY: AddressSanitizer: 48136 byte(s) leaked in 2 allocation(s).
```

### Steps to Reproduce
```
$ touch output.x
$/usr/local/bin/magick convert Memory-Leak-2 output.x
```
then close the windows of ImageMagick.

### System Configuration
<!-- Tell us about the environment where you are experiencing the bug -->

- ImageMagick version: 7.0.8-35
- Environment (Operating system, version and so on): Linux ubuntu 4.15.0-42-generic #45~16.04.1-Ubuntu SMP Mon Nov 19 13:02:27 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
- Additional information:

<!-- Thanks for reporting the issue to ImageMagick! -->
[memory_leaks_2.zip](https://github.com/ImageMagick/ImageMagick/files/3012281/memory_leaks_2.zip)

credit：
 ADlab of venustech

memory leaks in XCreateImage
This is a GitHub Issue
repo:ImageMagick
owner:ImageMagick
Title : memory leaks in XCreateImage
Issue date:

--- start body ---
### Prerequisites

- [x] I have written a descriptive issue title
- [x] I have verified that I am using the latest version of ImageMagick
- [x] I have searched [open](https://github.com/ImageMagick/ImageMagick/issues) and [closed](https://github.com/ImageMagick/ImageMagick/issues?q=is%3Aissue+is%3Aclosed) issues to ensure it has not already been reported

### Description
```
=================================================================
==15742==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 136 byte(s) in 1 object(s) allocated from:
    #0 0x7fadbfd0c79a in __interceptor_calloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x9879a)
    #1 0x7fadbcb0e220 in XCreateImage (/usr/lib/x86_64-linux-gnu/libX11.so.6+0x27220)

Indirect leak of 48000 byte(s) in 1 object(s) allocated from:
    #0 0x7fadbfd0c602 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x98602)
    #1 0x508cf3 in XMakeImage MagickCore/xwindow.c:5733
    #2 0x82940c in XConfigureImage MagickCore/display.c:4449
    #3 0x85e6bd in XDisplayImage MagickCore/display.c:15069
    #4 0x81b445 in DisplayImages MagickCore/display.c:1705
    #5 0x77475f in WriteXImage coders/x.c:202
    #6 0x808fb6 in WriteImage MagickCore/constitute.c:1226
    #7 0x8097ea in WriteImages MagickCore/constitute.c:1376
    #8 0xbb0499 in ConvertImageCommand MagickWand/convert.c:3305
    #9 0xc9c5ea in MagickCommandGenesis MagickWand/mogrify.c:184
    #10 0x40e941 in MagickMain utilities/magick.c:149
    #11 0x40eb22 in main utilities/magick.c:180
    #12 0x7fadbbffc82f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)

SUMMARY: AddressSanitizer: 48136 byte(s) leaked in 2 allocation(s).
```

### Steps to Reproduce
```
$ touch output.x
$/usr/local/bin/magick convert Memory-Leak-2 output.x
```
then close the windows of ImageMagick.

### System Configuration
<!-- Tell us about the environment where you are experiencing the bug -->

- ImageMagick version: 7.0.8-35
- Environment (Operating system, version and so on): Linux ubuntu 4.15.0-42-generic #45~16.04.1-Ubuntu SMP Mon Nov 19 13:02:27 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
- Additional information:

<!-- Thanks for reporting the issue to ImageMagick! -->
[memory_leaks_2.zip](https://github.com/ImageMagick/ImageMagick/files/3012281/memory_leaks_2.zip)

credit：
 ADlab of venustech

--- end body ---

Memory leaks detected in the XCreateImage function of ImageMagick version 7.0.8-35, which can lead to resource exhaustion and potential Denial of Service (DoS) if exploited in a long-running application.