toupper(c lowercase with no upper case) -> c not 0.

Reference: /n/atom/patch/applied/runetyperedux
Date: Thu Mar 13 17:24:18 CET 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/libc/port/runetype.c	Thu Mar 13 17:23:48 2014
+++ /sys/src/libc/port/runetype.c	Thu Mar 13 17:23:48 2014
@@ -31,7 +31,7 @@
 	if(p && c >= p[0] && c <= p[1])
 		return p[2] + (c - p[0]);
 	p = bsearch(c, __tolower1, nelem(__tolower1)/2, 2);
-	if(p && c == p[0])
+	if(p && c == p[0] && p[1] != 0)
 		return p[1];
 	return c;
 }
@@ -45,7 +45,7 @@
 	if(p && c >= p[0] && c <= p[1])
 		return p[2] + (c - p[0]);
 	p = bsearch(c, __toupper1, nelem(__toupper1)/2, 2);
-	if(p && c == p[0])
+	if(p && c == p[0] && p[1] != 0)
 		return p[1];
 	return c;
 }
@@ -56,7 +56,7 @@
 	Rune *p;
 
 	p = bsearch(c, __totitle1, nelem(__totitle1)/2, 2);
-	if(p && c == p[0])
+	if(p && c == p[0] && p[1] != 0)
 		return p[1];
 	return c;
 }