fixed regression in memory allocation routine

src/basic/basic_commands/cmd_let.s

@@ -273,8 +273,16 @@ cmd_let_assign_string_not_text_area:
 
 	// XXX
 
-	// No special case optimization is possible - alocate new memory area
+	// No special case optimization is possible
+	// Free the memory belonging to the old string
 
+	// XXX
+	// jsr varstr_free_DSCPNT_set
+
+
+	// And allocate memory for the new string
+
+	lda __FAC1+0
 	ldy #$00
 
 #if CONFIG_MEMORY_MODEL_60K
@@ -288,9 +296,6 @@ cmd_let_assign_string_not_text_area:
 
 #endif
 
-	lda __FAC1+0
-	sta (VARPNT), y
-
 	jsr varstr_alloc
 
 	// Copy the string
@@ -344,8 +349,4 @@ cmd_let_assign_string_not_text_area:
 
 #endif
 
-	// Free the memory of the old string
-
-	// XXX
-
 	rts