Fix RGBLINK assertion failure when -s and -c invalidly match (#2109)

src/gfx/main.cpp

@@ -671,24 +671,27 @@ int main(int argc, char *argv[]) {
 	autoOutPath(localOptions.autoPalettes, options.palettes, ".pal");
 	autoOutPath(localOptions.autoPalmap, options.palmap, ".palmap");
 
-	// Execute deferred pal spec parsing, now that all other params are known
-	switch (options.palSpecType) {
-	case Options::NO_SPEC:
-	case Options::EMBEDDED:
-		assume(!localOptions.palSpec);
-		break;
-	case Options::INLINE:
-		assume(localOptions.palSpec);
-		parseInlinePalSpec(localOptions.palSpec->c_str());
-		break;
-	case Options::EXTERNAL:
-		assume(localOptions.palSpec);
-		parseExternalPalSpec(localOptions.palSpec->c_str());
-		break;
-	case Options::DMG:
-		assume(localOptions.palSpec);
-		parseDmgPalSpec(localOptions.palSpec->c_str());
-		break;
+	// Execute deferred pal spec parsing, now that all other params are known.
+	// Do not parse pal specs if `options.nbColorsPerPal` is invalid.
+	if (options.nbColorsPerPal > 0 && options.nbColorsPerPal <= 4) {
+		switch (options.palSpecType) {
+		case Options::NO_SPEC:
+		case Options::EMBEDDED:
+			assume(!localOptions.palSpec);
+			break;
+		case Options::INLINE:
+			assume(localOptions.palSpec);
+			parseInlinePalSpec(localOptions.palSpec->c_str());
+			break;
+		case Options::EXTERNAL:
+			assume(localOptions.palSpec);
+			parseExternalPalSpec(localOptions.palSpec->c_str());
+			break;
+		case Options::DMG:
+			assume(localOptions.palSpec);
+			parseDmgPalSpec(localOptions.palSpec->c_str());
+			break;
+		}
 	}
 
 	verboseDo(VERB_CONFIG, verboseOutputConfig);

test/gfx/bad_pal_and_colors.err

@@ -0,0 +1,3 @@
+error: Palette size ('-s') must not exceed 4
+error: 2bpp palettes can only contain 4 colors, not 5
+Conversion aborted after 2 errors

test/gfx/bad_pal_and_colors.flags

@@ -0,0 +1 @@
+-s 5 -c #111,#222,#333,#444,#555