Fix TTXLine::validate properly this time (I hope)

known_services

@@ -10,4 +10,5 @@ SERVICEDATA=(\
   "Ceefax (Worldwide),svn,https://internal.nathanmediaservices.co.uk/svn/ceefax/Worldwide,Ceefax/regional,Ceefax" \
   "Ceefax (Yorks and Lincs),svn,https://internal.nathanmediaservices.co.uk/svn/ceefax/Yorks&Lincs,Ceefax/regional,Ceefax" \
   "Chunkytext,git,https://zxnet.co.uk/git/cf.git,Chunkytext," \
+  "SPARK,git,https://github.com/ZXGuesser/spark-teletext.git,SPARK," \
 )

ttxline.cpp

@@ -66,19 +66,23 @@ std::string TTXLine::validate(std::string const& val)
     std::string str="                                        ";
     for (unsigned int i=0;i<val.length() && j<40;i++)
     {
-        ch=val[i] & 0x7f;   // Convert to 7 bits
-        
-        if (ch==0x1b) // escape?
+        ch = val[i] & 0x7f; // 7-bit
+
+        if (val[i] == 0x1b) // ascii escape
         {
             i++;
-            ch=(val[i] & 0x3f);
+            ch = val[i] & 0x3f;
         }
-
-        if (ch==0)
+        else if (val[i] < 0x20) // other ascii control code
         {
-            ch=0x80; // set high bit to escape nulls in strings
+            break; // abort
         }
-
+
+        if (ch < 0x20)
+        {
+            ch |= 0x80; // set high bit on control codes
+        }
+
         str[j++]=ch;
     }
     return str;