ImageMagick has a heap buffer over-read via 32-bit integer overflow in MAT decoder

In MAT decoder uses 32-bit arithmetic due to incorrect parenthesization resulting in a heap over-read.

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==969652==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x506000003b40 at pc 0x555557b2a926 bp 0x7fffffff4c80 sp 0x7fffffff4c70
READ of size 8 at 0x506000003b40 thread T0