fix button overlap for multirow buttongroups

src/gui/css/options.css

@@ -21,6 +21,9 @@ div.options-group div.button-group {
 	/* left & right outline overlap each other so we don't have a double border */
 	outline: solid 2px var(--button-border-color);
 	margin-left: 2px;
+	/* half the outline width for multirow buttongroups */
+	margin-top: 1px;
+	margin-bottom: 1px;
 }
 
 .button-group button:hover {
@@ -74,7 +77,7 @@ div.options-group input {
 	min-width: unset; /* remove SC styling */
 	width: 12em;
 	/* move back so that the outline of a potential select overlaps in front */
-	position:relative;
+	position: relative;
 	z-index: 0;
 }