tweaks: strip four unneeded checks

The functions to read and write history files will not even be called
when the home directory is missing, so there is no need to check for
that eventuality again.

src/history.c

@@ -216,21 +216,17 @@ char *get_history_completion(filestruct **h, char *s, size_t len)
 }
 #endif /* ENSABLE_TABCOMP */
 
-/* Return the constructed dirfile path, or NULL if we can't find the home
- * directory.  The string is dynamically allocated, and should be freed. */
-char *construct_filename(const char *str)
+/* Return a dynamically-allocated path that is the concatenation of the
+ * user's home directory and the given name. */
+char *construct_filename(const char *name)
 {
-    char *newstr = NULL;
+    size_t homelen = strlen(homedir);
+    char *joined = charalloc(homelen + strlen(name) + 1);
 
-    if (homedir != NULL) {
-	size_t homelen = strlen(homedir);
+    strcpy(joined, homedir);
+    strcpy(joined + homelen, name);
 
-	newstr = charalloc(homelen + strlen(str) + 1);
-	strcpy(newstr, homedir);
-	strcpy(newstr + homelen, str);
-    }
-
-    return newstr;
+    return joined;
 }
 
 char *histfilename(void)
@@ -299,10 +295,6 @@ void load_history(void)
     struct stat hstat;
     FILE *histfile;
 
-    /* If no home directory was found, we can't do anything. */
-    if (histname == NULL || legacyhist == NULL)
-	return;
-
     /* If there is an old history file, migrate it. */
     /* (To be removed in 2018.) */
     if (stat(legacyhist, &hstat) != -1 && stat(histname, &hstat) == -1) {
@@ -390,10 +382,6 @@ void save_history(void)
 	return;
 
     histname = histfilename();
-
-    if (histname == NULL)
-	return;
-
     histfile = fopen(histname, "wb");
 
     if (histfile == NULL)
@@ -418,13 +406,7 @@ void save_history(void)
 void load_poshistory(void)
 {
     char *poshist = poshistfilename();
-    FILE *histfile;
-
-    /* If the home directory is missing, do_rcfile() will have reported it. */
-    if (poshist == NULL)
-	return;
-
-    histfile = fopen(poshist, "rb");
+    FILE *histfile = fopen(poshist, "rb");
 
     if (histfile == NULL) {
 	if (errno != ENOENT) {
@@ -491,12 +473,7 @@ void save_poshistory(void)
 {
     char *poshist = poshistfilename();
     poshiststruct *posptr;
-    FILE *histfile;
-
-    if (poshist == NULL)
-	return;
-
-    histfile = fopen(poshist, "wb");
+    FILE *histfile = fopen(poshist, "wb");
 
     if (histfile == NULL)
 	fprintf(stderr, _("Error writing %s: %s\n"), poshist, strerror(errno));