fixed crash in BASIC when trying to incorrectly execute operator

src/basic/basic_commands/cmd__jumptable.s

@@ -55,14 +55,12 @@
 	cmd_tab,                           // XXX this token probably does not belong here
 	do_SYNTAX_error,                   // 'TO' is not a standalone command
 	do_SYNTAX_error,                   // 'FN' is not a standalone command
-	cmd_spc,                           // XXX this token probably does not belong here
+	cmd_spc                            // XXX this token probably does not belong here
 	
 	// 'THEN' ($A7) and 'STEP' ($A9) are not standalone commands
 	// 'NOT' ($A8) is an operator, not a command
 
-	// $CB, but remapped to $A7
-
-	cmd_go
+	// 'GO' ($CB) is handled separately
 )
 
 

src/basic/engine_runtime/execute_line_statements.s

@@ -61,6 +61,9 @@ execute_statements:
 	cpx #$7F
 	bcc_16 execute_statements_var_assign         // not a token - try variable assign
 
+	cpx #$A7
+	bcs_16 do_SYNTAX_error
+
 #if !HAS_OPCODES_65C02
 
 	// Get the jump table entry for it, push it on the stack, and then RTS to start it.