gui: don't truncate values to 0 after scaling

Avoids invisible lines (e.g. input cursor) when scaling down.

Change-Id: I595e8bdb2fa468c30f104867ad77be2423ec287f
diff --git a/gui/gui.cpp b/gui/gui.cpp
index 35b33b1..f3d31d7 100644
--- a/gui/gui.cpp
+++ b/gui/gui.cpp
@@ -990,7 +990,10 @@
 extern "C" int scale_theme_x(int initial_x)
 {
 	if (scale_theme_w != 1) {
-		return (int) ((float)initial_x * scale_theme_w);
+		int scaled = (float)initial_x * scale_theme_w;
+		if (scaled == 0 && initial_x > 0)
+			return 1;
+		return scaled;
 	}
 	return initial_x;
 }
@@ -998,7 +1001,10 @@
 extern "C" int scale_theme_y(int initial_y)
 {
 	if (scale_theme_h != 1) {
-		return (int) ((float)initial_y * scale_theme_h);
+		int scaled = (float)initial_y * scale_theme_h;
+		if (scaled == 0 && initial_y > 0)
+			return 1;
+		return scaled;
 	}
 	return initial_y;
 }