Silence some -Wswitch-default warnings.

Source/Core/VideoBackends/OGL/ProgramShaderCache.cpp

@@ -55,9 +55,10 @@ static std::string GetGLSLVersionString()
 			return "#version 140";
 		case GLSL_150:
 			return "#version 150";
+		default:
+			// Shouldn't ever hit this
+			return "#version ERROR";
 	}
-	// Shouldn't ever hit this
-	return "#version ERROR";
 }
 
 void SHADER::SetProgramVariables()