fix broken f_file variable and add note to register funcs

include/mariebuild/mb_parse.h

@@ -38,7 +38,10 @@ typedef struct mb_file {
 void free_build_file(mb_file* file);
 
 /* Parsing Functions */
-
+/* NOTE: After using any of these registering functions, pointers to members 
+ *       of the targeted build-file need to be reassigned since registering 
+ *       breaks the old pointers.
+ */
 int register_sector(struct mb_file* file, char *name);
 int register_section(struct mb_sector* sector, char *name);
 int register_field(struct mb_section* section, char *name, char *value);

src/mb_execute.c

@@ -65,16 +65,16 @@ int mb_exec_compile(struct mb_build* build) {
     f_file = find_field(build->build_file, pfile_field);
   }
 
-  /*
-   * TODO: This breaks the "file" field and potentially some others,
-   * debug and fix (URGENT)
   char pmodeflags_field[] = ".config/mariebuild/mode_flags";
   mb_field *f_modeflags = find_field(build->build_file, pmodeflags_field);
   if (f_modeflags == NULL) {
     register_field(find_section(build->build_file, pmariebuild), "mode_flags"
                                                                , "");
+
+    // Reassing f_file because the original pointer gets broken by new field
+    // being registered.
+    f_file = find_field(build->build_file, pfile_field);
   }
-  */
 
   while (file != NULL) {
     if (f_file->value != NULL) free(f_file->value);