Ensure COLOR= gives Illegal Quantity Error for > 255. Fixes #30

basic.js

@@ -856,7 +856,7 @@ this.basic = (function() {
         if (!env.lores) { runtime_error('Lores graphics not supported'); }
 
         n = n >> 0;
-        if (n < 0) { runtime_error(ERRORS.ILLEGAL_QUANTITY); }
+        if (n < 0 || n > 255) { runtime_error(ERRORS.ILLEGAL_QUANTITY); }
 
         env.lores.setColor(n);
       },

samples/sample.unittests.txt

@@ -411,6 +411,10 @@
 7020 T$ = "COLOR="
 : T = 0 : U = 0 : FOR I = 0 TO 15 : COLOR= I : PLOT 0,0 : T = T + I : U = U + SCRN(0,0) : NEXT
 : S = (T=U) : GOSUB 1
+: T = 1 : ONERR GOTO 7022
+7021 COLOR=256
+: T = 2
+7022 S = (T=1) AND (PEEK(222)=53) : GOSUB 1
 
 7030 T$ = "PLOT"
 : COLOR= 5 : PLOT 0,0 : PLOT 39,0 : PLOT 0,47 : PLOT 39,47