Fix potential stack memory leak in gbagfx due to out of bounds read (#2162)

* fix(tools): gbagfx potential oob read

---------

Co-authored-by: sbird <sbird@no.tld>

tools/gbagfx/main.c

@@ -333,6 +333,9 @@ void HandleJascToGbaPaletteCommand(char *inputPath, char *outputPath, int argc,
 
             if (numColors < 1)
                 FATAL_ERROR("Number of colors must be positive.\n");
+            
+            if (numColors > 255)
+                FATAL_ERROR("Number of colors must be less than 256.\n");
         }
         else
         {