Fixed a few compiler warnings on clang (#3263)

Mostly pointer-bool-conversion and autological-pointer-compare

src/common/utils.cpp

@@ -240,7 +240,7 @@ void findfile(const char *p, const char *pat, void (func)(const char*))
 		sprintf(tmppath,"%s%c%s",path, PATHSEP, entry->d_name);
 
 		// check if the pattern matchs.
-		if (entry->d_name && strstr(entry->d_name, pattern)) {
+		if (entry->d_name[0] && strstr(entry->d_name, pattern)) {
 			func( tmppath );
 		}
 		// check if it is a directory.