Fix crash on resize

Prevent to realloc xw.specbuc with a negative number of col.
Add proper hints for the minimal size, for one character.

x.c

@@ -672,6 +672,8 @@ cresize(int width, int height)
 
 	col = (win.w - 2 * borderpx) / win.cw;
 	row = (win.h - 2 * borderpx) / win.ch;
+	col = MAX(1, col);
+	row = MAX(1, row);
 
 	tresize(col, row);
 	xresize(col, row);
@@ -681,8 +683,8 @@ cresize(int width, int height)
 void
 xresize(int col, int row)
 {
-	win.tw = MAX(1, col * win.cw);
+	win.tw = col * win.cw;
-	win.th = MAX(1, row * win.ch);
+	win.th = row * win.ch;
 
 	XFreePixmap(xw.dpy, xw.buf);
 	xw.buf = XCreatePixmap(xw.dpy, xw.win, win.w, win.h,
@@ -788,15 +790,17 @@ xhints(void)
 
 	sizeh = XAllocSizeHints();
 
-	sizeh->flags = PSize | PResizeInc | PBaseSize;
+	sizeh->flags = PSize | PResizeInc | PBaseSize | PMinSize;
 	sizeh->height = win.h;
 	sizeh->width = win.w;
 	sizeh->height_inc = win.ch;
 	sizeh->width_inc = win.cw;
 	sizeh->base_height = 2 * borderpx;
 	sizeh->base_width = 2 * borderpx;
+	sizeh->min_height = win.ch + 2 * borderpx;
+	sizeh->min_width = win.cw + 2 * borderpx;
 	if (xw.isfixed) {
-		sizeh->flags |= PMaxSize | PMinSize;
+		sizeh->flags |= PMaxSize;
 		sizeh->min_width = sizeh->max_width = win.w;
 		sizeh->min_height = sizeh->max_height = win.h;
 	}