Revert "common/common.c: extend xbasename(), xstrdup() and xrealloc() definition to return NULL if input was NULL (and log it) [#2052]"

This reverts commit 05610d1.
Seems to cause segfaults on its own, maybe something relied on
older behavior (non-NULLs returned in case of bad inputs?)
To investigate separately later...

Author: jimklimov

common/common.c

@@ -643,21 +643,11 @@ int sendsignal(const char *progname, const char * sig)
 
 const char *xbasename(const char *file)
 {
-	const char *p;
-#ifdef WIN32
-	const char *r;
-#endif
-
-	if (file == NULL) {
-		upsdebugx(1, "%s: got null input", __func__);
-		return NULL;
-	}
-
 #ifndef WIN32
-	p = strrchr(file, '/');
+	const char *p = strrchr(file, '/');
 #else
-	p = strrchr(file, '\\');
-	r = strrchr(file, '/');
+	const char *p = strrchr(file, '\\');
+	const char *r = strrchr(file, '/');
 	/* if not found, try '/' */
 	if( r > p ) {
 		p = r;
@@ -1739,14 +1729,7 @@ void *xcalloc(size_t number, size_t size)
 
 void *xrealloc(void *ptr, size_t size)
 {
-	void *p;
-
-	if (ptr == NULL) {
-		upsdebugx(1, "%s: got null input", __func__);
-		return NULL;
-	}
-
-	p = realloc(ptr, size);
+	void *p = realloc(ptr, size);
 
 	if (p == NULL)
 		fatal_with_errno(EXIT_FAILURE, "%s", oom_msg);
@@ -1755,14 +1738,7 @@ void *xrealloc(void *ptr, size_t size)
 
 char *xstrdup(const char *string)
 {
-	char *p;
-
-	if (string == NULL) {
-		upsdebugx(1, "%s: got null input", __func__);
-		return NULL;
-	}
-
-	p = strdup(string);
+	char *p = strdup(string);
 
 	if (p == NULL)
 		fatal_with_errno(EXIT_FAILURE, "%s", oom_msg);