Fix a crash when reporting an error at the end of a file

The compiler crashes with a segmentation fault when an unterminated
C-style comment exists at the very end of a file.

The root cause is a buffer over-read in the error() function, which
attempts to construct a diagnostic message by reading the source line
containing the error. When the error is on the last line of a file
without a trailing newline, this logic would read past the end of the
source buffer.

Fix the issue by adding a bounds check to the loop, ensuring it does
not read beyond the source buffer's size. This allows the compiler to
correctly report the "Unenclosed C-style comment" error instead of
crashing.

Author: visitorckw

src/globals.c

@@ -1395,7 +1395,8 @@ void error(char *msg)
     start_idx = offset + 1;
 
     for (offset = 0;
-         offset < MAX_SOURCE && SOURCE->elements[start_idx + offset] != '\n';
+         offset < MAX_SOURCE && (start_idx + offset) < SOURCE->size &&
+         SOURCE->elements[start_idx + offset] != '\n';
          offset++) {
         diagnostic[i++] = SOURCE->elements[start_idx + offset];
     }