Fixes sign mismatch warning in comparison.

TRAC #23714

Author: Shannon Woods
Signed-off-by: Jamie Madill

diff --git a/src/libGLESv2/Context.cpp b/src/libGLESv2/Context.cpp
index 27b0e7f..175bf83 100644
--- a/src/libGLESv2/Context.cpp
+++ b/src/libGLESv2/Context.cpp

@@ -3320,7 +3320,7 @@
         // Verified by the glDraw* functions
         ASSERT(count >= 0);
 
-        if (static_cast<unsigned short>(count) + 1 > (std::numeric_limits<unsigned short>::max() / sizeof(unsigned short)))
+        if (static_cast<unsigned short>(count) + 1u > (std::numeric_limits<unsigned short>::max() / sizeof(unsigned short)))
         {
             return error(GL_OUT_OF_MEMORY);
         }