fix for panic formatting imageset where there's only one colour in th…

…e source tile

vera/src/imageset.rs

@@ -650,6 +650,9 @@ fn find_optimal_range(
 		if max - min <= range as usize {
 			for i in 0..permutation.len() {
 				range_vals[i].1 = vec![usize::from_str_radix(permutation[i], 10)?];
+				if max == min {
+					break;
+				}
 			}
 			return Ok((true, min));
 		}

vera/tests/imageset.rs

@@ -343,3 +343,26 @@ fn imageset_pal_64_4bpp() -> Result<(), Error> {
 
 	Ok(())
 }
+
+/*#[test]
+fn imageset_crash() -> Result<(), Error> {
+	let test_png = include_bytes!("data/imageset/crash-test-pal.png");
+	let pal_config = VeraPaletteLoadConfig {
+		direct_load: true,
+		include_defaults: false,
+		sort: false,
+		..VeraPaletteLoadConfig::default()
+	};
+	let palette = VeraPalette::derive_from_png("pal", test_png.to_vec(), &pal_config)?;
+	println!("{}", palette);
+
+	let imageset_png = include_bytes!("data/imageset/crash-test-imageset.png");
+	let mut set = VeraImageSet::new("imageset_1", 16, 16);
+	let config = VeraImageSetLoadConfig::default();
+	set.load_from_png(imageset_png.to_vec(), &config)?;
+	set.format_indices(&palette, VeraPixelDepth::BPP4)?;
+	println!("{}", set);
+
+	Ok(())
+
+}*/