added edge cases for one or both numbers = 0

src/ggT/ggT.c

@@ -2,6 +2,14 @@
 
 
 int ggT(int a, int b){
+    if(a == 0 && b == 0){
+        return 0;
+    } else if(a == 0){
+        return b;
+    } else if(b == 0){
+        return a;
+    }
+
     while (b != 0) {
         int temp = b;
         b = a % b;