Prevent crashing when dumping binary files to terminal.

"cat"ing binary files often crashes Konsole.  This patch checks the
indicies.
Note that there are tons of 'undecodable sequences' that also print
out.  These likely should not be displayed unless debugging.
BUG: 184964
FIXED-IN: 4.8

src/Screen.cpp

@@ -659,6 +659,13 @@ void Screen::displayCharacter(unsigned short c)
             charToCombineWithX = cuX - 1;
             charToCombineWithY = cuY;
         }
+
+        // Prevent "cat"ing binary files from causing crashes.
+        if (charToCombineWithX >= screenLines[charToCombineWithY].size())
+        {
+            return;
+        }
+
         Character& currentChar = screenLines[charToCombineWithY][charToCombineWithX];
         if ((currentChar.rendition & RE_EXTENDED_CHAR) == 0)
         {