environment: fix segfault

Author: johanmalm

src/environment.cpp

@@ -35,6 +35,12 @@ QString environment_get(const char *key)
 
 void environment_set(const char *key, const char *value)
 {
+	if (!key || !*key) {
+		return;
+	}
+	if (!value || !*value) {
+		return;
+	}
     /* set cursor for labwc  - should cover 'replace' or 'append' */
     char xcur[4096] = { 0 };
     strcpy(xcur, key);