fix several bugs with storing BASIC lines

c64/basic/basic_main_loop.s

@@ -81,7 +81,8 @@ rsl_l1:	lda $0200,x
 	ora basic_fac1_mantissa+3
 	ora basic_fac1_exponent
 	beq +
-ml_bad_line_number:	
+ml_bad_line_number:
+	inc $0424
 	;; Syntax error
 	ldx #10
 	jmp do_basic_error
@@ -113,8 +114,18 @@ skip_spaces:
 	lda basic_fac1_mantissa+1
 	sta basic_line_number+1
 
+	lda basic_current_line_ptr+0
+	sta $0420
+	lda basic_current_line_ptr+1
+	sta $0421
+	
 	;; Delete line if present
 	jsr basic_find_line
+
+	lda basic_current_line_ptr+0
+	sta $0420
+	lda basic_current_line_ptr+1
+	sta $0421
 	
 	bcs +
 	jsr basic_delete_line