port fix for a segfault: stefan11111/kdrive@0aa5ca4

This fixes an incorrect loop condtion, as it is possible to skip over NUM_PROT when incrementing
This causes a segfault in kdrive, when km->i_prot would have to loop, instead continuing to read out of bounds.
I couldn't get tinyx to also segfault, but that doesn't mean it's impossible. It might happen on different hardware.

Author: stefan11111

kdrive/linux/mouse.c

@@ -729,6 +729,9 @@ static void MouseFirstProtocol(Kmouse * km, char *prot)
 			for (i = 0; i < NUM_PROT; i++)
 				ErrorF(" %s", kmouseProts[i]->name);
 			ErrorF("\n");
+			km->i_prot = 0;
+			km->prot = kmouseProts[km->i_prot];
+			ErrorF("Falling back to %s\n", km->prot->name);
 		} else {
 			km->prot = kmouseProts[km->i_prot];
 			if (km->tty && !km->prot->tty)
@@ -754,7 +757,7 @@ static void MouseNextProtocol(Kmouse * km)
 	do {
 		if (!km->prot)
 			km->i_prot = 0;
-		else if (++km->i_prot == NUM_PROT)
+		else if (++km->i_prot >= NUM_PROT)
 			km->i_prot = 0;
 		km->prot = kmouseProts[km->i_prot];
 	} while (km->prot->tty != km->tty);