QColorSpace destructor causes random crash on macOS

I keep getting random crashes on macOS like this:

Crashed Thread: 5 QThread

Exception Type: EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note: EXC_CORPSE_NOTIFY

Application Specific Information:
abort() called
XXXX(54496,0x700009b02000) malloc: Incorrect checksum for freed object 0x7f8de15dac00: probably modified after being freed.
Corrupt value: 0x0

Thread 5 Crashed:: QThreadThread 5 Crashed:: QThread
0   libsystem_kernel.dylib        0x00007fff7a21e2c2 __pthread_kill + 10
1   libsystem_pthread.dylib        0x00007fff7a2d9bf1 pthread_kill + 284
2   libsystem_c.dylib              0x00007fff7a1886a6 abort + 127
3   libsystem_malloc.dylib        0x00007fff7a297077 malloc_vreport + 545
4   libsystem_malloc.dylib        0x00007fff7a2afe0d malloc_zone_error + 183
5   libsystem_malloc.dylib        0x00007fff7a2935c8 small_free_list_remove_ptr_no_clear + 1177
6   libsystem_malloc.dylib        0x00007fff7a2927dc free_small + 853
7   org.qt-project.QtGui          0x000000010bea7a22 QColorSpacePrivate::~QColorSpacePrivate() + 66
8   org.qt-project.QtGui          0x000000010bea5bc3 QColorSpace::~QColorSpace() + 35
9   org.qt-project.QtGui          0x000000010bd2235c QImageData::~QImageData() + 108
10  org.qt-project.QtGui          0x000000010bd23e93 QImage::~QImage() + 51 
...

It happened after repeated calls like this on many image files:

QImage image(filename);

...some code to manipulate image pixel data directly...

QImageWriter writer(filename);
writer.setQuality(100);
writer.write(image);

It is unfortunately quite random but happens quite frequently. Both I and some of my users are getting this. Both on macOS 10.15.4 and 10.14.6. I'm wondering if anyone is aware of such issue.

A little more information if it can be helpful:

The crash is totally random. It may crash when loading an image file. But next time it would be fine loading the same file, but crash on another file. 

If I remove the code that manipulate the image pixel data directly, I can't seem to make it crash anymore! I'm really baffled...