add generic error in diskio.status() if drive status can't be read

compiler/res/prog8lib/diskio.p8

@@ -353,11 +353,15 @@ _end        rts
             messageptr++
         }
 
-io_error:
         @(messageptr) = 0
+done:
         c64.CLRCHN()        ; restore default i/o devices
         c64.CLOSE(15)
         return filename
+
+io_error:
+        filename = "?disk error"
+        goto done
     }
 
 

compiler/src/prog8/compiler/target/cpu6502/codegen/AsmGen.kt

@@ -128,7 +128,7 @@ internal class AsmGen(private val program: Program,
                 out("* = ${program.actualLoadAddress.toHex()}")
                 val year = LocalDate.now().year
                 out("  .word  (+), $year")
-                out("  .null  $9e, format(' %d ', _prog8_entrypoint), $3a, $8f, ' prog8 by idj'")
+                out("  .null  $9e, format(' %d ', _prog8_entrypoint), $3a, $8f, ' prog8'")
                 out("+\t.word  0")
                 out("_prog8_entrypoint\t; assembly code starts here\n")
                 if(!options.noSysInit)

examples/test.p8

@@ -1,10 +1,20 @@
 %import textio
+%import diskio
 %zeropage basicsafe
 
 main {
 
     sub start() {
 
+        txt.print(diskio.status(8))
+        txt.nl()
+        txt.print(diskio.status(9))
+        txt.nl()
+;        txt.print(diskio.status(10))
+;        txt.nl()
+;        txt.print(diskio.status(11))
+;        txt.nl()
+
         uword x=22
         x*=320
         txt.print_uw(x)