Fix panic when read/write out of bounds

[Robbepop]

Caught at #1553 via Wasmi's execution fuzzer:
https://github.com/wasmi-labs/wasmi/actions/runs/15998303367/job/45126754018?pr=1553

Test case: cargo run -p wasmi_cli <input>

(module
    (memory (;0;) i64 756615 (pagesize 0x1))
    (export "" (memory 0))
    (data (;0;) (i64.const -1) "{")
)

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.

Project coverage is 72.34%. Comparing base (8c4dcbe) to head (83dfc39).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/core/src/memory/mod.rs	66.66%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1554   +/-   ##
=======================================
  Coverage   72.33%   72.34%           
=======================================
  Files         179      179           
  Lines       16318    16320    +2     
=======================================
+ Hits        11803    11806    +3     
+ Misses       4515     4514    -1     

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