fragment shader also needs to define precision for sampler2DArray (#26853)

src/renderers/webgl/WebGLProgram.js

@@ -846,6 +846,7 @@ function WebGLProgram( renderer, cacheKey, parameters, bindingStates ) {
 		].join( '\n' ) + '\n' + prefixVertex;
 
 		prefixFragment = [
+			'precision mediump sampler2DArray;',
 			'#define varying in',
 			( parameters.glslVersion === GLSL3 ) ? '' : 'layout(location = 0) out highp vec4 pc_fragColor;',
 			( parameters.glslVersion === GLSL3 ) ? '' : '#define gl_FragColor pc_fragColor',