Revert "Fixed: Fatal error when a font is not set"

This reverts commit 5e2f924.

Attempting to perform any of these operations without a currently
active font is indeed a logic error. Subverting the fatal error is
not a solution.

doomsday/engine/src/render/rend_font.c

@@ -495,16 +495,11 @@ static int textFragmentWidth(const char* fragment)
     const char* ch;
     unsigned char c;
 
-    // Cannot determine height without a current font.
-    if(!fr.fontNum) return 0;
-
-    /*
     if(fr.fontNum == 0)
     {
         Con_Error("textFragmentHeight: Cannot determine height without a current font.");
         exit(1);
     }
-    */
 
     // Just add them together.
     len = strlen(fragment);
@@ -527,14 +522,11 @@ static int textFragmentHeight(const char* fragment)
     size_t len;
     uint i;
 
-    if(!fr.fontNum) return 0;
-
-    /*
     if(fr.fontNum == 0)
     {
         Con_Error("textFragmentHeight: Cannot determine height without a current font.");
         exit(1);
-    }*/
+    }
 
     // Find the greatest height.
     i = 0;