apply fix for #597 to neth

neth/main.cpp

@@ -379,10 +379,11 @@ int main(int argc, char** argv)
 				mining = ~(unsigned)0;
 			else if (isFalse(m))
 				mining = 0;
-			else if (int i = stoi(m))
-				mining = i;
 			else
-			{
+				try {
+					mining = stoi(m);
+				}
+				catch (...) {
 					cerr << "Unknown -m/--mining option: " << m << endl;
 					return -1;
 				}