Fix out-of-bounds in 'combine' texture modifier

Co-authored-by: tenplus1 <tenplus1@users.noreply.github.com>

util/convert.sh

@@ -0,0 +1,10 @@
+# inverts signs_lib font to black on transparent background
+img_path=./
+#img_results=./converted
+#mkdir -p $img_results
+for img in ${img_path}/*;
+    do 
+#    convert -negate $img ${img_results}/${img#./*};
+	convert $img -background white -alpha remove -alpha off -negate -transparent white $img
+done
+