GHSA-7rvh-xqp3-pr8j

### Summary Magick fails to check for circular references between two MVGs, leading to a stack overflow.

### Details

After reading mvg1 using Magick, the following is displayed: ``` ./magick -limit memory 2GiB -limit map 2GiB -limit disk 0 mvg:L1.mvg out.png AddressSanitizer:DEADLYSIGNAL ================================================================= ==3564123==ERROR: AddressSanitizer: UNKNOWN SIGNAL on unknown address 0x000000000000 (pc 0x5589549a4458 bp 0x7ffcc61f34a0 sp 0x7ffcc61efdd0 T0) #0 0x5589549a4458 in GetImagePixelCache MagickCore/cache.c:1726 #1 0x5589549b02c1 in QueueAuthenticPixelCacheNexus MagickCore/cache.c:4261 #2 0x5589549a2f24 in GetAuthenticPixelCacheNexus MagickCore/cache.c:1368 #3 0x5589549bae98 in GetCacheViewAuthenticPixels MagickCore/cache-view.c:311 #4 0x558954afb3a5 in DrawPolygonPrimitive._omp_fn.1 MagickCore/draw.c:5172 #5 0x7f62dd89fa15 in GOMP_parallel (/lib/x86_64-linux-gnu/libgomp.so.1+0x14a15) #6 0x558954ae0f41 in DrawPolygonPrimitive MagickCore/draw.c:5156 #7 0x558954ae5607 in DrawPrimitive MagickCore/draw.c:5875 #8 0x558954adc72d in RenderMVGContent MagickCore/draw.c:4522 #9 0x558954adcf67 in DrawImage MagickCore/draw.c:4561 #10 0x55895496cedb in RenderFreetype MagickCore/annotate.c:2065 #11 0x55895496702e in RenderType MagickCore/annotate.c:1112 #12 0x558954963da7 in AnnotateImage MagickCore/annotate.c:544 #13 0x558954ae4e0a in DrawPrimitive MagickCore/draw.c:5799 #14 0x558954adc72d in RenderMVGContent MagickCore/draw.c:4522 #15 0x558954adcf67 in DrawImage MagickCore/draw.c:4561 #16 0x558954755a46 in ReadMVGImage coders/mvg.c:240 #17 0x558954a15ecc in ReadImage MagickCore/constitute.c:743 #18 0x558954ae3c76 in DrawPrimitive MagickCore/draw.c:5705 #19 0x558954adc72d in RenderMVGContent MagickCore/draw.c:4522 #20 0x558954adcf67 in DrawImage MagickCore/draw.c:4561 #21 0x558954755a46 in ReadMVGImage coders/mvg.c:240 ... ```

### Impact This is a DoS vulnerability, and any situation that allows reading the mvg file will be affected.