TTF: avoid crashes on fonts without U+0041 LATIN CAPITAL LETTER A.

Since font sizes in SolveSpace are specified in terms of cap height,
we need U+0041 to determine cap height. Some fonts lack it; in
that case, we assume that cap height is the same as the size we've
requested. This avoids a crash, at the cost of completely wrong
(although consistent) metrics; I do not really know of a better way.

src/ttf.cpp

@@ -189,7 +189,8 @@ bool TtfFont::LoadFromFile(FT_Library fontLibrary, bool nameOnly) {
     if (gid == 0) {
         dbp("freetype: CID-to-GID mapping for CID 0x%04x failed: %s; using CID as GID",
             chr, ft_error_string(gid));
-        gid = chr;
+        dbp("Assuming cap height is the same as requested height (this is likely wrong).");
+        capHeight = (double)sizeRequest.height;
     }
 
     if(gid) {