ColorTransition: small fix backported from 291b181)

Author: cahirwpz

lib/libgfx/ColorTransition.c

@@ -5,6 +5,10 @@ u_short ColorTransition(u_short from, u_short to, u_short step) {
   short r = (from & 0xf00) | ((to >> 4) & 0x0f0) | step;
   short g = ((from << 4) & 0xf00) | (to & 0x0f0) | step;
   short b = ((from << 8) & 0xf00) | ((to << 4) & 0x0f0) | step;
-  
-  return (colortab[r] << 4) | colortab[g] | (colortab[b] >> 4);
+
+  r = colortab[r];
+  g = colortab[g];
+  b = colortab[b];
+
+  return (r << 4) | g | (b >> 4);
 }