simplify (greedy) font caching allocating a bit

POSIX says:
"If ptr is a null pointer, realloc() shall be equivalent to malloc() for the
 specified size."

x.c

@@ -1243,14 +1243,9 @@ xmakeglyphfontspecs(XftGlyphFontSpec *specs, const Glyph *glyphs, int len, int x
 			fontpattern = FcFontSetMatch(0, fcsets, 1,
 					fcpattern, &fcres);
 
-			/*
-			 * Allocate memory for the new cache entry.
-			 */
+			/* Allocate memory for the new cache entry. */
 			if (frclen >= frccap) {
 				frccap += 16;
-				if (!frc)
-					frc = xmalloc(frccap * sizeof(Fontcache));
-				else
 				frc = xrealloc(frc, frccap * sizeof(Fontcache));
 			}