[utils] `LoadFileData()` segfaults when dataSize param is `NULL`

[danielchasehooper]

Issue description

LoadFileData segfaults when dataSize param is NULL. It'd be more helpful if it returned NULL

Environment

macOS

Code Example

char *data = LoadFileData("file.txt", NULL);

[raysan5]

For most of the raylib functions is up to the user to validate the inputs, if raylib should consider all possible bad-use scenarios it would require reviewing most of the library functions and it will increase source-code complexity.

[raysan5]

It's up to the user to avoid this kind of bad-use cases, same issue will happen with most raylib functions receiving some pointer.

[vittorioromeo]

It's up to the user to avoid this kind of bad-use cases, same issue will happen with most raylib functions receiving some pointer.

@raysan5: raylib should at the very least assert in this case.